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advice for analogue measurement of tilt meter, run through voltage divider


Shanks.J Sep 15, 2020 03:05 PM

Hi there Peter,
I have a Gefran tilt meter/Inclinometer which puts out two signal voltages based on the two axis (X and Y) which is measures.
I am reading the voltages across the analogue inputs of a CR6. (Y axis u1 with u2 and X-axis U3 with U4)

The tilt meter without adjustment runs voltages from 0 - 10volts. 5 volts perfectly level, 10 volts +30degrees, 0volts -30degrees.


As the CR6 can only read voltages between 0-5v, I have run the sensor through a simple voltage divider across two equal resistors. This has cut the output voltages in half. This has worked well and the output voltages when read with the voltmeter are accurate and make sense, (0v -30degrees, 2.5v flat, 5v +30egrees).

unfortunately when I run this through my code the results I get do not make sense. Andy voltage below 2.5v are accurate, but anything above 2.5 volts comes out as limited or reverse charge. Values that should be read as 4 volts or 3.5 volts for example come back as 2.7 or even 1.2volts.

I am using Volt Diff at this stage to read the voltages. I cannot use VoltSE as the negative end of the sensor also runs through the voltage divider ( using a known ground takes the signal value back into the higher ranges of 0-10).
initially the plan was to use a multiplier and offset to get the value in degrees, but for not it is easier to read the volts as they come out for problem-solving purposes.

Is there something happening in the code to cause this? Is there a reaction to my simple voltage divider that I’m not understanding?

Open to you valued advice, attached is my simple code
 


'Declare Variables and Units

Public BattV
Public PTemp_C
Public X_Axis
Public Y_Axis

Units BattV=Volts
Units PTemp_C=Deg C
Units Y_Axis=mV
Units X_Axis=mV


'Define Data Tables
DataTable(Table1,True,-1)
DataInterval(0,60,Min,10)

Sample(1,X_Axis,FP2)

Sample(1,Y_Axis,FP2)
EndTable

'Main Program
BeginProg 'Main Scan Scan(5,Sec,1,0)
'Default CR6 Datalogger Battery Voltage measurement 'BattV'
Battery(BattV)
'Default CR6 Datalogger Wiring Panel Temperature measurement 'PTemp_C'
PanelTemp(PTemp_C,60)
'Generic Differential Voltage measurements 'DiffVolt'
VoltDiff(Y_Axis,1,mV5000,U1,True,500,60,1,0)
'Generic Differential Voltage measurements 'DiffVolt_2'
VoltDiff(X_Axis,1,mV5000,U3,True,500,60,1,0)
'Call Data Tables and Store Data
CallTable Table1 NextScanEndProg


aks Sep 16, 2020 11:18 AM

Please e mail me your wiring diagram and any other relevant information to me, I have sent you an e mail asking for the same.

Thanks

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