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VOLT108 / VOLT116 4-wire PT100

HMNIBIO Jan 28, 2020 02:57 AM


the Volt-modules are fairly new, so I find it quite hard to find help. So far, the module commands seem not to be supported in CRBasic Editor even (?).

I want to connect 4-wire Pt100-modules to them. As far as I understand it with my limited understanding of the theory, a 4WPB100-module or corresponding resistors and the PRTCalc-instruction should be used. Derived from code generated in shortcut for a CDM A108 module, the code should then look something like this

'Generic Half Bridge, 4 Wire measurements 'HBr4W' on VOLT108 with CPI address 1

PRTCalc (temp_from_Volt108,1,HBr4W,1,1.0,0)

Is that correct?

JDavis Jan 28, 2020 09:29 AM

Code generated for a CDM-A108 should work for a VOLT108, as long as the CPIAddModule instruction is removed from the program, and you put the right module type like you have done.

These modules are able to do current excitation, so you can actually read a PT100 without adding resistors. The measurement to use is CDM_Resistance().

A new version of ShotCut with support for the VOLT108 will be released soon. The modules are included in CRBasic already, if you install the most recent vesion of the datalogger OS on your computer. The help files and compile in CRBasic are updated when you run the datalogger OS .exe file on your computer.

HMNIBIO Jan 29, 2020 12:10 AM

Great, thank you very much! On the one hand, I have bought resistors in vain. On the other hand, life is much easier now. Have installed the latest Cr1000x OS, and all instructions are there, as you promised.

HMNIBIO Feb 4, 2020 03:09 AM

Follow up question: Connecting a K&Z CNR4 to a Volt116.

wire colours black, black, white, gree, yellow, gray, brown.

Both thermistor and Pt100-measurements should be possible without additional resistors. Is this correct? Are CDM_Resistance (Pt100) and CDM_Therm109 (thermistor) the correct instructions, and how should these be wired?

My code so far, but no success

CDM_Resistance (VOLT116,3,CNR4_Pt100,1,mV5000,2,X1,1,2500,True ,True ,0,50,1.0,0)

CDM_Therm109 (VOLT116,3,CNR4_thermistor,1,1,X1,0,50,1.0,0)

Best regards,


JDavis Feb 4, 2020 09:17 AM

CDM_Resistance would be the correct instruction for either sensor in the CNR4.

CDM_Therm109 is expecting the particular thermistor in a model 109 temperature sensor.

HMNIBIO Feb 5, 2020 07:39 AM

Excellent. Figured it out for the Pt100.

Just out of interest: Can the thermistor can be measured at the same time? I wired

white - Hi

black - Lo

with grey in the excitation channel from before. Values are +/-0, though. 



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