"Richard Smith" wrote in message ...

Pressure gauge which is removable - connect in line, only when needed
- when doing something which does need a measurement - a test or a
tensioning activity.
Has hydraulic couplings and can be there in-line, or can be absent.

Question - would one pump and one cylinder, a 50Tonne 50mm stroke
single-acting, be enough for now? Strategy completed by --- get two
pressure gauges, one to 700+Bar, one to say 100Bar, so can accurately
read off the pressure for both high-force and low-force tests?

Can you think of a solution to a problem of recording the maximum
pressure at which the sample broke?

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When I built custom industrial test stations I used a Greenlee hydraulic
knockout set to punch holes in steel boxes for controls and conduit. The
combination of a heavy cylinder and hand pump on opposite ends of a stiff
springy hose is impossible to fully control with only two hands, and the
free end hits hard when it falls. Even when working on the floor the pump or
cylinder tended to flip over hard enough to damage an attached gauge.

I'd say that the pump, cylinder and gauge are enough to get started, and the
modular Porta-Power system is easy to expand later as needed. In my steel
scrap collection is a press-like rectangular frame someone made from 1.250"
hydraulic piston rod joining two drilled steel bars. Do you have a
thread-cutting lathe and milling machine to make similar fixturing? Messing
with hydraulics quickly took me beyond what a bandsaw, drill press and
welder could do, although I bought all the high pressure fittings.

I had to machine a retainer for the low profile hydraulic cylinder of the
10,000 Lb force gauge I added to my sawmill, and repair the pressure gauge
on a tire inflater that a springy hose pulled off the sawmill when I was
away.

I assembled a cheap and simple data logger for slowly changing signals from
an old laptop and meters like this:
https://tekpower.us/multimeter/digit.../tp4000zc.html
For my solar power application the optical isolation between channels is
vital. If you acquire a pressure sensor with an analog voltage or current
output the meter's .CSV data file can be read into a spreadsheet and easily
converted to match your calibration measurement.

There are inexpensive DRO (distance) scales available to retrofit machine
tools but I've never tried to connect one to a computer.

As first a chemist and later an electronic test tech I learned how to make
measurements to 0.01%, and also that there's no point trying to greatly
exceed the accuracy of your worst instrument or the inherent randomness of
your subject. In non-critical mechanical testing 5% accuracy is good enough,
which might be 20% of the full gauge scale although higher than half scale
is preferable.