mA loop to direct temperature measurement on a PicoLog 1216 w/small terminal board

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LabTech
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mA loop to direct temperature measurement on a PicoLog 1216 w/small terminal board

Post by LabTech » Fri Apr 12, 2019 3:47 pm

Greetings all!

I'm am new to these PicoLog devices and liking them the more I use them. I am currently trying to connect a Vaisala HMT335 Temp/Humid device to the PicoLog 1216 w/small terminal board. My superior has expressed an interest in tying this device in with our other inputs from the devices under test in order to have one output data file instead of having to merge files. The question is, What settings/formula(s) are required to convert the 4-20 mA output of the Vaisala temperature humidity device to display temperature changes in degrees Celsius on the PicoLogs display graph?

Gerry
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Joined: Mon Aug 11, 2014 11:14 am

Re: mA loop to direct temperature measurement on a PicoLog 1216 w/small terminal board

Post by Gerry » Tue Apr 16, 2019 2:34 pm

Hi LabTech,

What you need to do is connect a 120 ohm resistor across the terminal board connections (as shown on page 7 of the Small Terminal Board User Guide here: https://www.picotech.com/download/manua ... -guide.pdf) that will connect to the input you will be using on the PicoLog 1216, to convert the 4-20mA into 480-2,400mV. Then you can use custom scaling, in the channel input of the PicoLog 1216, to display the correct Temperature values for the equivalent loop current values, as follows:
In PicoLog 6, for the PicoLog 1216, select the input that the 4-20mA loop current will be passing through, and click on 'Advanced', then click in the 'Probe or scaling' text box to open the 'Probes and Custom Scaling' window. Select 'Table', click in the large red box, then type the following:
0.48 x
2.4 y
where x is the Temperature that corresponds to the minimum loop current of 0mA
and where y is the Temperature corresponding to the maximum loop current of 20mA
Finally click in the 'Return units' text box to select temperature from the drop down list.

Regards,

Gerry
Gerry
Technical Specialist

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