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Enviromon "drifting values" EL005 / EL037s

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Enviromon "drifting values" EL005 / EL037s

Postby kensong » Mon Dec 08, 2008 2:50 pm

Hello again,

As before, I have 1 EL005, 2x EL037's (adressed as 11 & 12).
Measuring 3x Temperatures and 3x Pressures, Temps on EL037(11) in ch1,2 & 3, Pressures on EL037(12) in Ch 1,2 & 3. Field devices are Danfoss MBS / MBT types, using 4-20 mA and wired as shown. Using box power.

The values seem to just hang around (@7ma), with 1 or 2 occassionally drifting up to 23(ish) mA. Because pressure current will always rise when Temp current falls (they are inverse of one another). I calculated that each "pair" will only ever use a maximum of ~22mA, ~66mA in total. However some of the power may be used by the EL037's.

Has anyone seen this "indeterminate drifting effect"?
Is it just a lack of power (exceeding the 100mA)?
In which case do I just whack the 24vDC on and re-wire the module ends?

(Yes I did a bench test with 1 of each sensor and one EL037, it seemed to work, but if it is obviously just power, you can just say "yes Mr Thickie, it is" and tell me that the 24vDC is the solution and I'll get on with it).
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Postby ziko » Wed Dec 10, 2008 3:57 pm

Each converter should take nominally 10mA, so you should be drawing approx 20mA out of the converters. Since you are using the network voltage to supply the sensors this will affect your overall network current as you correctly said is a max of 100mA.

It generally is better to power your transducers by an external source.

Kind regards.

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