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looking for K type multimeter, and thermistor
hi
I don't have any electronics background I am looking for a multimeter with a K-Type plug socket, And a Thermistor with wires going to a K-Type connector so it can plug into it. I will get a table of resistance to temperature, with the thermistor. so I can measure the temperature of things. I tried calling maplin technical(0906... thus expensive), but they said they no longer sell K-Type multimeters. They prob know alot. He said he thinks any multimeter with K-Type plug would support thermistors and thermocouples. He suggested I try RS components. I tried RS components technical (0845..). She mentioned a multimeter. It was extortionate - Fluke 179. £211, or £266 calibrated. The calibrated one comes with bead type thermocouple. She said she doesn't know if it supports thermistors too. The description only mentioned thermocouple. I asked her - aren't they usually about £20. She then mentioned another range that was £40, but I said forget it. Does anybody know of a multimeter that does what I want? Am I looking at the right price range? £20. Or should I be looking at £40? More than £40 is really too much. There are cheap multimeters I have seen at maplin at one time, going for 6 quid, just not with K-Type sockets. thanks |
looking for K type multimeter, and thermistor
wrote in message ... hi I don't have any electronics background I am looking for a multimeter with a K-Type plug socket, And a Thermistor with wires going to a K-Type connector so it can plug into it. I will get a table of resistance to temperature, with the thermistor. so I can measure the temperature of things. I tried calling maplin technical(0906... thus expensive), but they said they no longer sell K-Type multimeters. They prob know alot. He said he thinks any multimeter with K-Type plug would support thermistors and thermocouples. He suggested I try RS components. I tried RS components technical (0845..). She mentioned a multimeter. It was extortionate - Fluke 179. £211, or £266 calibrated. The calibrated one comes with bead type thermocouple. She said she doesn't know if it supports thermistors too. The description only mentioned thermocouple. I asked her - aren't they usually about £20. She then mentioned another range that was £40, but I said forget it. Does anybody know of a multimeter that does what I want? Am I looking at the right price range? £20. Or should I be looking at £40? More than £40 is really too much. There are cheap multimeters I have seen at maplin at one time, going for 6 quid, just not with K-Type sockets. thanks As far as I am aware , a type K refers to a thermocouple not a thermistor, they are different in the way they measure temperature. A thermocouple generates a voltage which changes with temperature. A thermistor does not generate a voltage it exhibits a resistance which changes with temperature. What is it you trying to measure the temperature of and how critical is the size of the sensor. If you were trying to measure the surface temperature of a small grass leaf for example, you could not use a large sensor because it would interfere with the actual temperature of the leaf. You also would have to shield the sensor from external radiation (sunlight or a strong beam of light) So please tell us what you want to do with it. Regards Don |
looking for K type multimeter, and thermistor
We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember " saying something like: Does anybody know of a multimeter that does what I want? Am I looking at the right price range? £20. Or should I be looking at £40? More than £40 is really too much. There are cheap multimeters I have seen at maplin at one time, going for 6 quid, just not with K-Type sockets. There are plenty of temp measuring DVMs around at twenty quid. I've got a couple that use K - plugs, dead cheap and they are accurate enough for my purposes. Irrc, CPC supplied them a couple of years ago. -- Dave GS850x2 XS650 SE6a "It's a moron working with power tools. How much more suspenseful can you get?" - House |
looking for K type multimeter, and thermistor
On 22 May, 17:01, "Donwill" popple @diddle .dot wrote:
wrote in message ... hi I don't have any electronics background I am looking for a multimeter with a K-Type plug socket, And a Thermistor with wires going to a K-Type connector so it can plug into it. I will get a table of resistance to temperature, with the thermistor. so I can measure the temperature of things. I tried calling maplin technical(0906... thus expensive), but they said they no longer sell K-Type multimeters. *They prob know alot. He said he thinks any multimeter with K-Type plug would support thermistors and thermocouples. He suggested I try RS components. I tried RS components technical (0845..). She mentioned a multimeter. It was extortionate - Fluke 179. * £211, or £266 calibrated. * The calibrated one comes with bead type thermocouple. *She said she doesn't know if it supports thermistors too. The description only mentioned thermocouple. *I asked her - aren't they usually about £20. She then mentioned another range that was £40, but I said forget it. Does anybody know of a multimeter that does what I want? Am I looking at the right price range? £20. *Or should *I be looking at £40? More than £40 is really too much. There are cheap multimeters I have seen at maplin at one time, going for 6 quid, just not with K-Type sockets. thanks As far as I am aware , a type K refers to a thermocouple not a thermistor, ok that makes sense.. I heard it refers to type of metal.. and that thermocouple has 2 different types of metal, to create a voltage difference. they are different in the way they measure temperature. A thermocouple generates a voltage which changes with temperature. A thermistor does not generate a voltage it exhibits a resistance which changes with temperature.. I know.. I don't mind measuring resistance and using a table. or measuring voltage and using a table or reading the temperature off an LCD display that displays temperature. What is it you trying to measure the temperature of and how critical is the size of the sensor.snip this one measuring a hard drive temperature (so in that pic, the small sensor goes on the black circle at the bottom of the hard drive. just off center. Quite a small sensor) http://www.overclockersclub.com/revi.../images/12.htm and maybe also this one measuring cpu temperature http://www.overclockersclub.com/revi...y/images/9.htm The [end of that] probe there looks long and tweezer like. I wonder if there are names for the different ends. |
looking for K type multimeter, and thermistor
On 22 May, 16:13, "
wrote: I am looking for a multimeter with a K-Type plug socket, Sounds expensive. Try RS or the on-line lab equipmented suppliers instead and get a dedicated lab temperature meter that uses a K type thermocouple. These are really pretty cheap these days. Get some spare thermocouples too. Simple ones are cheap, bare wire ones are easily broken. One of the easiest ways to break a thermocouple is to try removing or installing it from equipment where you'd have been a lot better off just buying and installing more of them in the first place and leaving them alone once installed. |
looking for K type multimeter, and thermistor
In message , Harry
Bloomfield writes wrote on 22/05/2008 : hi I don't have any electronics background I am looking for a multimeter with a K-Type plug socket, K-type is a thermocouple, K-type is the most common thermocouple and the type most commonly used for multi-meters. One should cost you just a couple of pounds or so, but you may need to source a suitable plug. Yeah but don't forget, the cable used to connect the thermocouple will also affect the readings. The OP needs to specify the approximate temperature range he expects to see (0-100c etc.) and then maybe we can work out what he actually needs. -- Clint Sharp |
looking for K type multimeter, and thermistor
In message , Donwill
writes wrote in message ... hi I don't have any electronics background I am looking for a multimeter with a K-Type plug socket, And a Thermistor with wires going to a K-Type connector so it can plug into it. I will get a table of resistance to temperature, with the thermistor. so I can measure the temperature of things. Does the OP want something like this ? http://cpc.farnell.com/jsp/level5/mo...cpc/403321.xml -- geoff |
looking for K type multimeter, and thermistor
On Thu, 22 May 2008 18:15:19 +0100, Grimly Curmudgeon wrote:
Irrc, CPC supplied them a couple of years ago. Toolstation do the Laser brand ones. Not very accurate though. -- John Stumbles I forgot to take my amnesia medecine again |
looking for K type multimeter, and thermistor
On Thu, 22 May 2008 08:13:31 -0700 (PDT), "
wrote: I will get a table of resistance to temperature, with the thermistor. so I can measure the temperature of things. Nooooooooooooooooooo ! Type K refers to a type of thermocouple, this is a device formed from a junction of 2 dissimilar metals. It gives a voltage which varies according to the difference in temp. over the whole circuit so you need to know the ambient temp to start with. However the multimeter typically does all that for you. I tried calling maplin technical(0906... thus expensive), but they said they no longer sell K-Type multimeters. They prob know alot. Yes, about toy plastic helicopters and ghetto blasters :((( Take a look here : http://www.maplin.co.uk/module.aspx?...48318&doy=22m5 £16.99 This has what they describe as a temperature test function. This might do what you want. He said he thinks any multimeter with K-Type plug would support thermistors Unlikely. and thermocouples. Type K only, there are others. He suggested I try RS components. I tried RS components technical (0845..). She mentioned a multimeter. It was extortionate - Fluke 179. £211, or £266 calibrated. The calibrated one comes with bead type thermocouple. She said she doesn't know if it supports thermistors too. The description only mentioned thermocouple. I asked her - aren't they usually about £20. She then mentioned another range that was £40, but I said forget it. Does anybody know of a multimeter that does what I want? Am I looking at the right price range? £20. Or should I be looking at £40? More than £40 is really too much. There are cheap multimeters I have seen at maplin at one time, going for 6 quid, 2 for a fiver even. just not with K-Type sockets. There's more than just the socket involved. DG |
looking for K type multimeter, and thermistor
On Thu, 22 May 2008 22:51:30 +0100, Derek Geldard wrote:
On Thu, 22 May 2008 08:13:31 -0700 (PDT), " wrote: I will get a table of resistance to temperature, with the thermistor. so I can measure the temperature of things. Nooooooooooooooooooo ! snip Agreed... Found one at Rapid! http://www.rapidonline.com/Tools-Fas...quipment/Test- Equipment/Multimeters/5-in-1-Digital-multimeter/79188 Seems to measure everything, but I don't know what accuracy is required. -- Mick (Working in a M$-free zone!) Web: http://www.nascom.info http://mixpix.batcave.net Filtering everything posted from googlegroups to kill spam. |
looking for K type multimeter, and thermistor
In article
, wrote: hi I don't have any electronics background I am looking for a multimeter with a K-Type plug socket, And a Thermistor with wires going to a K-Type connector so it can plug into it. I will get a table of resistance to temperature, with the thermistor. so I can measure the temperature of things. Why a K-type connector? I have two multimeters that measure temperature - a Maplin and a Fluke and they both use standard banana plugs for the probe lead. I tried calling maplin technical(0906... thus expensive), but they said they no longer sell K-Type multimeters. They prob know alot. He said he thinks any multimeter with K-Type plug would support thermistors and thermocouples. He suggested I try RS components. I tried RS components technical (0845..). She mentioned a multimeter. It was extortionate - Fluke 179. £211, or £266 calibrated. The calibrated one comes with bead type thermocouple. She said she doesn't know if it supports thermistors too. The description only mentioned thermocouple. I asked her - aren't they usually about £20. She then mentioned another range that was £40, but I said forget it. Does anybody know of a multimeter that does what I want? Am I looking at the right price range? £20. Or should I be looking at £40? More than £40 is really too much. I'd check on Ebay. Loads of different multimeters on sale there and some will do temperature. Not sure about the socket, though. There are cheap multimeters I have seen at maplin at one time, going for 6 quid, just not with K-Type sockets. thanks -- *When it rains, why don't sheep shrink? * Dave Plowman London SW To e-mail, change noise into sound. |
looking for K type multimeter, and thermistor
On May 22, 8:29*pm, Clint Sharp wrote:
In message , Harry Bloomfield wrote on 22/05/2008 : hi I don't have any electronics background I am looking for a multimeter with a K-Type plug socket, K-type is a thermocouple, K-type is the most common thermocouple and the type most commonly used for multi-meters. One should cost you just a couple of pounds or so, but you may need to source a suitable plug. Yeah but don't forget, the cable used to connect the thermocouple will also affect the readings. The OP needs to specify the approximate temperature range he expects to see (0-100c etc.) and then maybe we can work out what he actually needs. -- Clint Sharp 0-100C Not sure what wires to buy with the thermocouple.. I have heard that a thermocouple needs to be plugged into a special socket for it.. e.g. K-Type thermocouple into a socket for K-Type thermocouples. So the multimeter geoff linked to wouldn't do it.. I didn't see that socket on it.. though the picture was not big. How about using a thermistor instead.. 'cos if that doesn't require any special socket, wouldn't it be better? I will call that company geoff and donwill and perhaps others too, have mentioned. That CRC company. Their lines will be open tomorrow.. thanks |
looking for K type multimeter, and thermistor
On May 22, 10:51*pm, Derek Geldard wrote:
On Thu, 22 May 2008 08:13:31 -0700 (PDT), " wrote: I will get a table of resistance to temperature, with the thermistor. so I can measure the temperature of things. Nooooooooooooooooooo ! Type K refers to a type of thermocouple, this is a device formed from a junction of 2 dissimilar metals. It gives a voltage which varies according to the difference in temp. over the whole circuit so you need to know the ambient temp to start with. However the multimeter typically does all that for you. thanks.. I understand now.. about the Type-K(which I see only applies as a type of thermocouple), and I see the difference between thermistor and thermocouple. But shouldn't I be able to use a thermistor with a multimeter? With a table of resistance to temperature. I tried calling maplin technical(0906... thus expensive), but they said they no longer sell K-Type multimeters. *They prob know alot. Yes, about toy plastic helicopters and ghetto blasters *:((( Take a look here : *http://www.maplin.co.uk/module.aspx?...48318&doy=22m5 £16.99 very interesting find, thanks snip |
looking for K type multimeter, and thermistor
On May 22, 11:25*pm, "Dave Plowman (News)"
wrote: In article , * wrote: hi I don't have any electronics background I am looking for a multimeter with a K-Type plug socket, And a Thermistor with wires going to a K-Type connector so it can plug into it. I will get a table of resistance to temperature, with the thermistor. so I can measure the temperature of things. Why a K-type connector? I have two multimeters that measure temperature - a Maplin and a Fluke and they both use standard banana plugs for the probe lead. my mistakes... my understanading now is that K-Type is a type of thermocouple. Multimeters need a special socket , the the female connector of it is i think some standard connector thermocouples with leads use. The socket's innards have to be for that specific type of thermocouple being used e.g. Type-K. Is it possible that your probe is a thermistor not a thermalcouple.. I am wondering if maybe thermocouples don't need a special plug.. or even special wires. So it may be easier with a thermistor. So.. I would agree with your question really.. of why a K-Type connector. Or rather, why a thermocouple - why not a thermistor? snip I'd check on Ebay. Loads of different multimeters on sale there and some will do temperature. Not sure about the socket, though. snip good point.. though the advantage of these electronics places is they have techical support telephone lines. |
looking for K type multimeter, and thermistor
I'd check on Ebay. Loads of different multimeters on sale there and some will do temperature. Not sure about the socket, though. There are cheap multimeters I have seen at maplin at one time, going for 6 quid, just not with K-Type sockets. thanks Agreed. EBay is your friend, here. A first search of "k-type" (a Freudian slip of entering x-type initially provided very very different results) shows on first page digital thermometers with 2 k-type thermocouples thrown in for £21 (inclusive of P&P) from our friends in China. Further down the pages plenty of spare thermocouples for around £5 each inclusive of P&P. If you can wait the couple of weeks for shipping then it's a simple no-brainer rather than trying to deal with the high-street or CPC (maybe they're good with tech support over the phone?, all I know is living close by, I've stormed out from their trade counter after 50 minutes of being given the wrong items) |
looking for K type multimeter, and thermistor
On 23 May, 00:18, "
wrote: Not sure what wires to buy with the thermocouple.. Thermocouple wires. Special magic ones, from the same shop as the thermocouple. I have heard that a thermocouple needs to be plugged into a special socket for it.. e.g. K-Type thermocouple into a socket for K-Type thermocouples. Yes. Anything with a K type socket can reasonably be assumed to work interchangeably with K type thermocouples, whether this is a temeprature meter, a multimeter that also does temperature, a fridge, oven, kiln or hamster-cosy. Anything using banana plugs, jacks or phonos is most likely using thermistors or semiconductor sensors, not thermocouples. There are also two sorts of K type connector. Old ones were yellow, new ones are green. They're not interchangeable, but you can convert equipment by swapping the plugs and socket. Remember that polarity is crucial! You won't convert a standard meter (voltage or current) to read a thermocouple without sufficint extra work to make it impractical, or sufficient knowledge to appreciate why it's not a practical idea. My K-type reader cost a tenner or so. They're really not expensive these days. |
looking for K type multimeter, and thermistor
wrote in message ... hi I don't have any electronics background I am looking for a multimeter with a K-Type plug socket, http://www.rapidonline.com/Tools-Fas...r/31051/kw/328 I have a couple of these in my electronics lab. It does come with a probe, which plugs in to the small rectangular green bit near the bottom right hand side of the meter. |
looking for K type multimeter, and thermistor
On Thu, 22 May 2008 23:25:41 +0100, Dave Plowman (News) wrote:
snip Why a K-type connector? I have two multimeters that measure temperature - a Maplin and a Fluke and they both use standard banana plugs for the probe lead. snip Because the output from the thermocouple is polarised it uses a special polarised connector on installed systems. There are also standards for the type (& colours!) of thermocouple connecting wire as this affects accuracy of the reading. You need to use Type K wire with a type K thermocouple for example. Using standard banana plugs may be acceptable if your thermocouple is local to the instrument. Ref: http://www.picotech.com/applications/thermocouple.html -- Mick (Working in a M$-free zone!) Web: http://www.nascom.info http://mixpix.batcave.net Filtering everything posted from googlegroups to kill spam. |
looking for K type multimeter, and thermistor
submitted this idea :
0-100C Not sure what wires to buy with the thermocouple.. I have heard that a thermocouple needs to be plugged into a special socket for it.. e.g. K-Type thermocouple into a socket for K-Type thermocouples. So the multimeter geoff linked to wouldn't do it.. I didn't see that socket on it.. though the picture was not big. There is nothing special about the socket, other than the electronics at the rear of the socket (the meter's electronics) are calibrated for a K-type. It does of course also need to be connected the correct way. The cable also need needs to be the correct type for best accuracy, but those probes designed for such use will already be fitted with a short lead anyway. If you use a thermistor ( can't see why you would want to), then your meter will not provide a direct temperature reading - you will have some maths to do to convert from the reading to a temperature. -- Regards, Harry (M1BYT) (L) http://www.ukradioamateur.co.uk |
looking for K type multimeter, and thermistor
Andy Dingley explained on 23/05/2008 :
My K-type reader cost a tenner or so. They're really not expensive these days. As did mine from Mr Maplin and that included the K-type probe with built in LCD display meter. -- Regards, Harry (M1BYT) (L) http://www.ukradioamateur.co.uk |
looking for K type multimeter, and thermistor
In article ,
mick wrote: Why a K-type connector? I have two multimeters that measure temperature - a Maplin and a Fluke and they both use standard banana plugs for the probe lead. snip Because the output from the thermocouple is polarised it uses a special polarised connector on installed systems. There are also standards for the type (& colours!) of thermocouple connecting wire as this affects accuracy of the reading. You need to use Type K wire with a type K thermocouple for example. Using standard banana plugs may be acceptable if your thermocouple is local to the instrument. Well, test leads on a multimeter are polarised too (by colour) for certain operations but are interchangeable. I don't think you'll damage a K-type sensor with reverse polarity. -- *How do they get the deer to cross at that yellow road sign? Dave Plowman London SW To e-mail, change noise into sound. |
looking for K type multimeter, and thermistor
On 23 May, 16:47, Harry Bloomfield
wrote: submitted this idea : 0-100C Not sure what wires to buy with the thermocouple.. I have heard that a thermocouple needs to be plugged into a special socket for it.. e.g. K-Type thermocouple into a socket for K-Type thermocouples. So the multimeter geoff linked to wouldn't do it.. I didn't see that socket on it.. though the picture was not big. There is nothing special about the socket, other than the electronics at the rear of the socket (the meter's electronics) are calibrated for a K-type. It does of course also need to be connected the correct way. The cable also need needs to be the correct type for best accuracy, but those probes designed for such use will already be fitted with a short lead anyway. I guess numbers on the LCD should indicate it in some obvious way. Thanks... I am really sorted now, in terms of information. I know what to look for. I know the terminology. I can see ones from maplin, I can also try CRC and ebay. I can get multimeters with temperature dispaying LCDs from maplin... that use - I think - diodes (which seem similar to thermistors and thermoprobes). And with ones that display temp, I don't need to do any conversions. I can look at CRC and ebay for multimeters or DVMs with K-Type socket.. that just display voltage You've all been extremely helpful. many thanks If you use a thermistor ( can't see why you would want to), then your meter will not provide a direct temperature reading - you will have some maths to do to convert from the reading to a temperature. -- now-just out of curiousity.. similarly with a thermocouple surely.. Just your meter from maplin has a temperature reading.. so I guess a chip in there converts voltage to temperature. An equivalent meter with thermistor, would have a chip that converts resistance to temperature. so howcome all focus is in thermocouples? do the multimeters with temperature readings not tend to use thermistors? I don't see mention of K-Type Thermocouple for N73CG , UT50C They do mention Diode though. so in defence of maplin tech. Maybe they really aren't selling multimeters with K-Type thermocouples anymore. |
looking for K type multimeter, and thermistor
formulated the question :
so howcome all focus is in thermocouples? do the multimeters with temperature readings not tend to use thermistors? I don't see mention of K-Type Thermocouple for N73CG , UT50C They do mention Diode though. so in defence of maplin tech. Maybe they really aren't selling multimeters with K-Type thermocouples anymore. A thermistor is not suitable for the higher temperatures which would cause it irreparable damage. A diode can be used to measure temperature, but its again its junction could suffer permanent damage above say 70 - 100 deg C. K-types are good (from memory) to in excess of 700 to 1000 deg C. -- Regards, Harry (M1BYT) (L) http://www.ukradioamateur.co.uk |
looking for K type multimeter, and thermistor
On Fri, 23 May 2008 17:00:59 +0100, Dave Plowman (News) wrote:
In article , mick wrote: Why a K-type connector? I have two multimeters that measure temperature - a Maplin and a Fluke and they both use standard banana plugs for the probe lead. snip Because the output from the thermocouple is polarised it uses a special polarised connector on installed systems. There are also standards for the type (& colours!) of thermocouple connecting wire as this affects accuracy of the reading. You need to use Type K wire with a type K thermocouple for example. Using standard banana plugs may be acceptable if your thermocouple is local to the instrument. Well, test leads on a multimeter are polarised too (by colour) for certain operations but are interchangeable. I don't think you'll damage a K-type sensor with reverse polarity. You won't damage it, but the temperature will read as a negative value! Remember that a thermocouple is a voltage source. You are (basically) using the meter as a voltmeter. A thermistor, on the other hand, isn't polarity sensitive because it is simply a resistor whose value changes with temperature. A thermocouple is far more difficult to read (linearly) but handles a wider temperature range. -- Mick (Working in a M$-free zone!) Web: http://www.nascom.info http://mixpix.batcave.net Filtering everything posted from googlegroups to kill spam. |
looking for K type multimeter, and thermistor
On 23 May, 17:00, "Dave Plowman (News)" wrote:
I don't think you'll damage a K-type sensor with reverse polarity. The pins are different widths (and different metals). Physically plugging it in backwards will break it (if you force it) and it certainly won't work. |
looking for K type multimeter, and thermistor
On 23 May, 16:47, Harry Bloomfield
wrote: There is nothing special about the socket, other than the electronics at the rear of the socket (the meter's electronics) are calibrated for a K-type. There's a lot special about that socket, mostly what the pins are made of. Then it's unusual and polarized to stop you mis-plugging it with anything else, or backwards. |
looking for K type multimeter, and thermistor
In article
, Andy Dingley wrote: I don't think you'll damage a K-type sensor with reverse polarity. The pins are different widths (and different metals). Physically plugging it in backwards will break it (if you force it) and it certainly won't work. Read the whole of the post you replied to. -- *Before they invented drawing boards, what did they go back to? Dave Plowman London SW To e-mail, change noise into sound. |
looking for K type multimeter, and thermistor
On 23 May, 17:33, "
wrote: similarly with a thermocouple surely.. Just your meter from maplin has a temperature reading.. so I guess a chip in there converts voltage to temperature. An equivalent meter with thermistor, would have a chip that converts resistance to temperature. There's a more fundamental difference too. Thermocouples only measure a temperature _difference_, thermistors measure an absolute temperature. A thermocouple meter used to measure around "room temperature" must also do something called "cold junction compensation", where it applies a suitable offset to compensate for the temperature that the meter end is at. This is tricky to do well. One way is to _know_ the cold junction temperature, by sticking it into melting ice or some fairly standard temperature. Another electronic way is to buy a chipset from Burr-Brown or similar that does the hard work for you. Of course if the thermocouple is measuring a high temperature such as a kiln, then the few degrees either way for the room temperature end is neither here nor there. Room temperature is usually constant within a few tens of degrees, or else the wetware complains. This is one reason why thermocouples are still popular for high temperature work, but the low temperature stuff was largely taken over by thermistors (from 20 years ago), and these days by semiconductor sensors (less sensitive to connection-induced errors). |
looking for K type multimeter, and thermistor
On 23 May, 23:49, "Dave Plowman (News)" wrote:
I don't think you'll damage a K-type sensor with reverse polarity. The pins are different widths (and different metals). Physically plugging it in backwards will break it (if you force it) and it certainly won't work. Read the whole of the post you replied to. If you physically plug a K type in backwards, you'll snap something. This might not be "reverse polarity" causing the damage, but you've buggered it up all the same. |
looking for K type multimeter, and thermistor
In article
, Andy Dingley wrote: I don't think you'll damage a K-type sensor with reverse polarity. The pins are different widths (and different metals). Physically plugging it in backwards will break it (if you force it) and it certainly won't work. Read the whole of the post you replied to. If you physically plug a K type in backwards, you'll snap something. This might not be "reverse polarity" causing the damage, but you've buggered it up all the same. If you read my post you'd see I was referring to my two meters which use K type sensors which plug into the normal banana plug sockets. Like every other DVM I've seen which does temperature measurement. There's simply no reason to provide a special socket for the temperature function on these since the sensor can't be damaged by wrong connection. Of course it won't work properly - but the plugs on the sensor are colour coded so that's hardly a problem. -- *Why is the third hand on the watch called a second hand? Dave Plowman London SW To e-mail, change noise into sound. |
looking for K type multimeter, and thermistor
On 27 May, 12:04, "Dave Plowman (News)" wrote:
If you read my post you'd see I was referring to my two meters which use K type sensors which plug into the normal banana plug sockets. You wrote "standard banana plugs for the probe lead.", not "piece of inaccurate crap that's so badly designed as to run thermocouple signals through banana plugs". I didn't realise you even meant thermocouples here - there are plenty of packaged thermometer probes around that will give a nice simple voltage output so they work with any meter (or measure rpm, or windspeed, or pH etc.). These quite rightly use bananas. Fluke do (or did anyway) make an adapter for fitting K types to bananas, but it's a bad idea. It's a particularly bad idea for low temperatures not much different from the temperature of the meter housing. The problem that it isn't a thermocouple any more, it's a daisy chain of several thermocouples. You're as likely to be measuring temperature differences from how warm the meter is, rather than the junction you want. If Fluke build a decent thermocouple cold junction front end and package it into a meter behind standard jacks (Why? K sockets aren't expensive) then it probably works OK for a kiln, but I wouldn't trust it below boiling water temperatures. Assuming that such an adapter plugged into a simple voltmeter would be any more than a random number generator would certainly be a mistake. If the contact resistance goes high and the meter impedance is that of a DVM front end, you'll just be measuring contact noise, not the couple's output at all. |
looking for K type multimeter, and thermistor
In article
, Andy Dingley wrote: If you read my post you'd see I was referring to my two meters which use K type sensors which plug into the normal banana plug sockets. You wrote "standard banana plugs for the probe lead.", not "piece of inaccurate crap that's so badly designed as to run thermocouple signals through banana plugs" One of them is a Fluke. And it certainly isn't 'inaccurate crap' A DVM with a temperature measuring function wouldn't necessarily be of the same design as a device meant solely for that purpose. Otherwise it would have sockets scattered all over the place. BTW - what's so special about a K type plug - apart from being polarised? I've seen expensive temperature measuring devices designed for building into machinery where the connections to the probe are simply screw terminals... -- *Hard work has a future payoff. Laziness pays off NOW. Dave Plowman London SW To e-mail, change noise into sound. |
looking for K type multimeter, and thermistor
On 27 May, 13:46, "Dave Plowman (News)" wrote:
One of them is a Fluke. And it certainly isn't 'inaccurate crap' Measuring temperatures comparable to the meter housing, it will be. It might not be inaccurate in use, but only because the valid range of use is limited to only measuring much higher temperatures. Like I said, I wouldn't trust this below boiling water. To be honest, this is the bane of thermocouples anyway. The single most useful lesson I learned from a whole degree in applied physics is that you don't trust any measurement based on comparing the differences between two very similar direct measurements. Your inaccuracies become proportionately far more important, relative to the measurement value you're after. This is why cold-junction compensation is so important and hard to design with competently, and why so many thermocouple-based measurements of lower temperatures are woefully inaccurate. I've worked on one site where switching a $50 input board for a $10 input board (flakey cold junction design) and a "saving" was then costing about $50k over a year in wasted energy - just from bad measurements off a thermocouple. They even had spreadsheets (based off that same thermocouple) to show how much they were now "saving" in energy. Funny thing is the fuel bills didn't reflect this. BTW - what's so special about a K type plug - apart from being polarised? Pins are made of matching metals to the wires. This avoids creating extra Seebeck junctions other than where you're measuring, and the single cold junction you're keeping a careful eye on. I've seen expensive temperature measuring devices designed for building into machinery where the connections to the probe are simply screw terminals... Yes, provided that the screws and receptacles are made of the right alloys (or at least plated with them). One of the attractions of a K type is that the metals used are affordable and mechanically suitable for doing this with. |
looking for K type multimeter, and thermistor
In article
, Andy Dingley wrote: One of them is a Fluke. And it certainly isn't 'inaccurate crap' Measuring temperatures comparable to the meter housing, it will be. It might not be inaccurate in use, but only because the valid range of use is limited to only measuring much higher temperatures. Like I said, I wouldn't trust this below boiling water. It's as accurate as needed at room temperature - measured against a mercury thermometer. I wouldn't expect it to be accurate to within a few decimal places though. I'd suggest you try one before spouting off. ;-) -- *I'm pretty sure that sex is better than logic, but I can't prove it. Dave Plowman London SW To e-mail, change noise into sound. |
looking for K type multimeter, and thermistor
On 27 May, 16:46, "Dave Plowman (News)" wrote:
I'd suggest you try one before spouting off. ;-) I suggest you learn how a thermocouple works before believing that a brandname badge on the front will make physics work differently for that maker's products. |
looking for K type multimeter, and thermistor
In article
, Andy Dingley wrote: I'd suggest you try one before spouting off. ;-) I suggest you learn how a thermocouple works before believing that a brandname badge on the front will make physics work differently for that maker's products. You suggested that my Fluke is useless at anything less than about 100C. You're wrong. Just live with it. -- *Vegetarians taste great* Dave Plowman London SW To e-mail, change noise into sound. |
looking for K type multimeter, and thermistor
wrote in message ... On May 22, 8:29 pm, Clint Sharp wrote: In message , Harry Bloomfield wrote on 22/05/2008 : hi I don't have any electronics background I am looking for a multimeter with a K-Type plug socket, K-type is a thermocouple, K-type is the most common thermocouple and the type most commonly used for multi-meters. One should cost you just a couple of pounds or so, but you may need to source a suitable plug. Yeah but don't forget, the cable used to connect the thermocouple will also affect the readings. The OP needs to specify the approximate temperature range he expects to see (0-100c etc.) and then maybe we can work out what he actually needs. -- Clint Sharp 0-100C What accuracy and/or precision http://en.wikipedia.org/wiki/Thermocouple in their picture they have the same meter I have by the looks of it. http://www.rapidonline.com/Tools-Fas...D%20multimeter at under £20 including the probe, but don't expect accuracy of 0.01C trust it to be within a a couple of Cs. I've tried the two I have here swapping the thermocouples around gives a range of readouts between 18C & 21C. The meters themselves seem to be about 1-2C difference with no probe connected. What are yougoing to use it for, my use was to test the temerature of an electric cookers oven as teh numbers on teh dial had all been wiped away. I checked it with another oven and setting the oven temp to 200C got meter results between 196C and 203C or there abouts which I thought was accurate enough for my use. Not sure what wires to buy with the thermocouple.. I have heard that a thermocouple needs to be plugged into a special socket for it.. e.g. K-Type thermocouple into a socket for K-Type thermocouples. The rapid meter 328 comes with the theremocouple no lead(s) required. (includes socket too) How about using a thermistor instead.. 'cos if that doesn't require any special socket, wouldn't it be better? Not really, as you'd have to construct a circuit for it. The meter has a switch position 'calibrated' for the thermocouple so just read the Cs of the scale direct. |
looking for K type multimeter, and thermistor
On May 28, 5:09*pm, "whisky-dave" wrote:
wrote in message ... On May 22, 8:29 pm, Clint Sharp wrote: In message , Harry Bloomfield wrote on 22/05/2008 : hi I don't have any electronics background I am looking for a multimeter with a K-Type plug socket, K-type is a thermocouple, K-type is the most common thermocouple and the type most commonly used for multi-meters. One should cost you just a couple of pounds or so, but you may need to source a suitable plug. Yeah but don't forget, the cable used to connect the thermocouple will also affect the readings. The OP needs to specify the approximate temperature range he expects to see (0-100c etc.) and then maybe we can work out what he actually needs. -- Clint Sharp 0-100C What accuracy and/or precision http://en.wikipedia.org/wiki/Thermocouple in their picture they have the same meter I have by the looks of it.http://www.rapidonline.com/Tools-Fas...quipment/Test-... at under £20 including the probe, but don't expect accuracy of 0.01C trust it to be within a a couple of Cs. I've tried the two I have here swapping the thermocouples around gives a range of *readouts between 18C & 21C. The meters themselves seem to be about 1-2C *difference with no probe connected. What are yougoing to use it for, my use was to test the temerature of an electric cookers oven as teh numbers on teh dial had all been wiped away. *I checked it with another oven and setting the oven temp to 200C got meter results between 196C and 203C or there abouts which *I thought was accurate enough for my use. hard drive temp.. ideally would want a flat shaped piece of metal that I can tape to the hard drive. The place to measure, apparently is on the bottom, there is this black circular area. A small bit of flat metal will do. Like this http://www.overclockersclub.com/revi.../images/12.htm Not sure what wires to buy with the thermocouple.. I have heard that a thermocouple needs to be plugged into a special socket for it.. e.g. K-Type thermocouple into a socket for K-Type thermocouples. The rapid meter 328 comes with the theremocouple no lead(s) required. (includes socket too) I see, from rapidonline.com http://www.rapidonline.com/Tools-Fas...eter/31051/kw/ I am glad I am getting more options... They all seem to involve the multimeter with the LCD screen, looks like the way things are done.. I don't see many options in types of probe though.. Fair enough, K-Type thermocouple probe But the contact at the end.. Ideally, I would like it to be like in that picture. BTW, how did you measure in the oven, did you stick the probe to the outside? How did you not burn the jacket of the wire? How about using a thermistor instead.. * 'cos if that doesn't require any special socket, *wouldn't it be better? Not really, as you'd have to construct a circuit for it. The meter has a switch position 'calibrated' for the thermocouple so just read the Cs of the scale direct.- with a table with C and resistance, it should be fine though, right? no need for a circui/chip to do the conversion. I assume this is the circuit you refer to. |
looking for K type multimeter, and thermistor
On 28 May, 22:12, "
wrote: BTW, how did you measure in the oven, did you stick the probe to the outside? How did you not burn the jacket of the wire? Either bare wires, well separated, or else you use a rigid metal tube probe, packed full with mineral (electrical) insulation and the wires separated inside. If you make your own rigid probes, the trick is to first glue the wires into a "stick" of wire + filler + wire on a piece of thin paper, all held together with waterglass. Once dry, burn the paper off with a small blowtorch. You can pack this rigid but fragile gluestick (carefully) into the tube without shorting anything out, then pack more filler round it. Don't place a thermocouple near an induction-heated crucible, or bad stuff happens... |
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