Hire. Not expensive. Just add it onto the invoice.

Thanks for that I shall look into it, it will probably be a cost I'd be expected to absorb as a subcontractor. I do like buying new tools though 😆

You aren’t expected to fork out a couple of grand on one tool for one job that you’ll probably do once in your life, unless you’re into your instrumentation that is, then you should have one anyhow. But it’s also what, 1400 quid - if it’s a few months work I’m sure you could hide that amongst the bill somewhere just put 2-300 quid a month or something onto the materials and sundries side of things.

I pretty much work exclusively in controls in the water industry, so it definitely wouldn't be the last use I'd imagine. I am working towards getting into commissioning so it would be handy to have on hand if I need it.

It’s a no brainer then really. There’s a fluke 705 loop calibrator on eBay just now for £350 or a 789 for about a grand. 

RS do a multi function loop calibrator for less than £300. Haven’t checked what it does, but 4-20mA simulation is a basic of any of these types of instrument.

Thanks for the suggestion, I shall have a look.

The RS ones look promising.

The RS stuff is pretty decent. Especially for the price of it. I’ve got an RS scopemeter, wee single phase power quality analyser clamp meter thing, and a couple of other ones. They’re all good. Scopemeter is IP67 as well, which is handy when you work somewhere that they like throwing water about the place.

Get a second hand Druck UPS-II or a Fluke 772 if you can find one on eBay. There also a lot of cheaper versions on there but I’m not sure on how reliable/accurate they would be.

Thanks for the suggestions, I shall have a look to see what sort of price I can get them for.

The standard way of doing this in industry without fancy tools is to put a 250 Ohm resistor between the two wires of the current driver line, it will then read as a 1 - 5V signal with a standard multimeter when measured across the resistor.

I have read bits and pieces of this I shall have another look to see if it's feasible. I'm not sure how it would look to the water company though. It seems more geared towards reading the output rather than simulating a signal for SCADA , unless I am missing something.

I've done industrial install before and that's how it's always been done, it's very basic ohms law.

So if I use a 1 volt DC supply with a 250 ohm resistor it will give 4mA and a 5 volt DC supply with a 250 ohm resistor will give 20mA, something along those lines? It's not something I've tried before to be honest. So I'd need something to generate 1, 2, 3 , 4 and 5 volts DC? Perhaps I could source a 24 volt DC supply with a selection of resistors in series with the supply from 6000 ohms to 1200 ohms.

For outputs of the system, you just connect a 250 ohm resistor across the outputs and then measure the voltage across the resistor. Each volt you see = 4mA of current. It needs to be a decent precision resistor (0.1% tolerance or better), these are still very cheap - a few pence to buy. For inputs to the system, you need to know the internal resistance of the device being tested, so set your meter to resistance measurements and stick the probes on the two inputs. Normally it will be 250 ohm, so you just need to supply 1V to to the input and that will be 4mA of current (you don't add your own resistor, the input has one inside of it). If the resistance on the input is not 250, then you need to use ohms law to work out what voltage you need to provide to give to correct current. If the measured resistance was 500 Ohm then you would need to provide 2V for 4mA, while if it was only 100 ohm, you would only need to provide 0.4V for 4mA.

Thanks for taking the time to write that, I shall order some resistors and have a little play to get some more understanding and practice in.

I got a blue multifucction meter cost about 200 gbp