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voltage to force translation ?

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jani12

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A transducer or sensor is connected to Force measurement unit. When force is applied to sensor, Sensor Developments Inc. PMAC 2000 Force measurement unit displays the Force in Newtons.

On back of PMAC 2000 unit, there is 9-pin I/O Connector. Please find description of this connector attached. My interest is Analog Output pins from this connector. I need to connect these Analog Output Pins to my Microcontroller based embedded application. My target Microcontroller A/D is 10-bit and A/D Reference Voltage is 5V.

Please check my connection as follows:

AOUT - (Pin 4) connects to unused Analog Pin in my microcontroller.
AOUT + (Pin 2) connects to different unused Analog Pin in my microcontroller.

Do I need to connect GND (Pin 3) to Ground on my target board ?

My understanding is that sum of AOUT+ and AOUT- is 5V. In my embedded software, how should I calculate voltage, should I simply subtract AOUT- from AOUT+ ?
What is the translation of voltage to force in Newtons ? What voltage is what amount of force ?

The attached description says AOUT+ is driven positive or negative with respect to AOUT- . Please provide examples of some AOUT+ and
AOUT- voltages I will see on my Microcontroller Analog Inputs ? I don't think I can have negative voltages going into my Analog Pins on my Microcontroller because A/D reference voltage in my microcontroller is 5V. So, I believe Analog Input values going into my
microcontroller need to be 0V to 5V. If yes, how do I know PMAC 2000 will send Analog Voltages in between 0 to 5V ?

Attached is also the manual for PMAC 2000 Force Unit.

On page 28 of the manual, please explain following:
"The Output impedance of each is 620 ohms and the output voltage is +1.0V nominal for 2mV/V full scale sensor.
What is 2mV/V ? Is this a typo ?
 

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KlausST

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Hi,

The information is a bit confusing, therefore I can't answer directely to the given data.

But to the sensor connections i can give some informations. It seems that the sensor is a ratiometric one, maybe a strain gauge sensor.
It usually has 4 connections. Two for supply and two for outputs. In the datasheet you will find informations on restance, supply voltage, full scale load and full scale outputs.
Maybe you supply it with 5V DC.
Then the given output of 2mV/V (no typo) says that output voltage at max load is 2mV/V x 5V = 10mV.
The 10mV is the difference of both outputs, but the absolute level is at about supplyvoltage/2. Here 2.5V.

The outputvoltage is relatively low, so you will need an amplifier before an ADC.

Klaus
 

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