INA125: INA125 reference circuit value of LOAD

Hi Fabian,

Happy to help! Unfortunately, your image didn't come through, I am unable to click on it. Can you try attaching it again using the "attachment" option in the editor?

-Tamara

Hi Fabian,

Can you reload your image? I am unable to view  the image. 

Question: Furthermore I want to ask when I have to connect V- ? 

I am not sure that I understand your question. You have to connect V-, the input is differential measurement.  Wheatston Bridge input circuit in Figure 10 is a balanced input circuit.  When the circuit is perfect balanced, the output is 0 or Vin+ = Vin- = 5V (input reference voltage = 10V) in Figure 10. The Gain of the circuit is shown in Equation 1. 

Regarding the Load: If the load is reference to ground as shown in Figure 10, the output voltage swing is limited to approx. 150mV. Then you are able to calculate the Gain through the equation below in red, shown in Figure 10. The selection of output current can be calculated in the bottom of p.7 datasheet via Output Voltage (V) vs. Output Current (mA) plot, which depending on your operating temperature. Once you know the output current, you can calculate the load resistance, 150mV/output_current (mA).

Best,

Raymond

Thanks for the answer.

Load: In my data sheet wasn't a figure 10, did you refer to  figure 1 ?
I added a Microcontroller in the picture with ADC on it. This should be correct as
I showed it, is it? What happens if I don't ad a resistor (Load) in parallel to the ADC input?

V-:  The question was concerning to pin 3 (V-) . When I understood you the right way
     you talked about V_in-(Pin 7) . Is this possible?

Output voltage swing: Is this the maximum difference between pin 6 and 7 ?

Best regards

Fabian

Hi Fabian,

If you are using MCU to read Vo at pin 11 of INA125, it will be easier to use single supply bridge amplifier, see Figure 5 in the previous reply. Your output voltage swing will be limited to approx. 150mV above ground. V- or pin 3 of INA125 will be connected to Ground as shown in Figure 5. Your will convert Vo+ to ADC of Micro controller, and Vo- connection is not needed, since the the measurement will be respect to GND. 

If you are using MCU as load,  then you do not need the Load Resistor shown in the drawing. 

Best,

Raymond

Hi Fabian,

I forgot to mention that the MCU needs to have the same ground as INA125, If you are using the single power supply operation, what is your voltage rail. I am trying to increase your output voltage swing, so that you will have better ADC resolution during voltage conversion. 

Best,

Raymond

MCU has same ground as INA125. Voltage rail of ADC Microcontroller is 2.5V . As Powersuply for the bridge I use 2,5 V of INA125 (Pin14).

I made a new picture of the schematic. Would this work? Do you see any problems? Is voltage swing limited in this schematic?