transducers and probes, the differences?

[bill1983]

when replacing a pressure transducer with an operating range of 4 - 20 ma, can i use any transducer with the same range even if the wiring is different? does anybody know enough about these or can direct me to a suitable source of education. in a similar vein, what are the differences between pt1000 probes from different manufacturers? what is the easiest way to test the most common probes?

[Frikkie]

Pressure transducers can use different systems to measure pressure like inductive, capacitive etc. I think you will need to use the same type of transducer.

PT1000 probes all measure 1000 ohms at 0 degrees celcius and their resistance will vary with temperature on the same linear scale. The differences are with the wiring system they use, some use 2 wires, some use 3 wires and some 4 wires so you must choose one with the same type of wiring.

[Peter_1]

4-20 mA is 4-20 mA. You must supply a voltage to a transducer and this transducer will modulate the current very precisely according tho the pressure, whatever voltage you connect, within limits of transducer,(mostly 5 to 24 VDC)
PT100 or PT1000, 2 wires are connected direct to the resistance element in the probe and the 3th wire is connected in parallel with 1 wire to measure the resistance over the whole length of the wire and subtract electronically this resistance to measure finally correctly the resistance in the probe it selves.
Either for the 4-20mA transducer or the PT1000, you can interchange brands. PT 100 is a standard, so is an 4-20 mA. You can have also 0-20 mA but then you can't detect cable fault.

[goshen]

hi there one of the best answers i have seen !!!!!

[coolhibby1875]

whilst i agree with peter about probes pt1000 you can use most brands however when fitting 4-20 MA transducers i would disagree as very recently in a m@s site i replaced a 2 cable alco transducer with a 2 cable carell and it didnt work very well changed with new alco and it worked perfect this was on a rdm pack controller.
then last week whilst on call i had a 4-20MA danfoss transducer on a danfoss controller pack in, I only had a eliwell 4-20MA transducer and it didnt work, so i removed a danfoss 1 from a redundant pack fitted it and it worked a charm?

[Peter_1]

Some 4-20mA needs an additional supply voltage.
Carel, Eliwell are interchangeable. Danfoss probes don't need neither an additional voltage.
We've changed Carel with Danfoss already, you just have to watch that the range of the transducer is exactly the same.

[bill1983]

coolhibby, sounds like your van stock is like mine, all sorts to get the job done, but not the same part as was fitted.
the reason i asked the question, was that one of our engineers was having trouble whilst interchanging transducers between an rdm and a siemens logo backup. both were 3 wire and i was told that both were 4-20mA. he couldn't get the logo transducer to read lower than 2 bar. i ended up visiting site myself, only to find that the logo transducer was 0 - 10v dc and not 4-20mA. problem solved.
i have learned more however by posing the question, so not a wasted exercise.
thanks for your input.

[coolhibby1875]

hi bill i had this same problem with the seimans logo that was fitted into a space pack in a sainsburys