XTR111: XTR111

Hi PJ,

can you show us a schematic? Where is the input signal coming from?

Kai

Hi PJ,

To use this device you need to scale the input signal into a more appropriate range. The easiest way to do this is to use a single op amp stage to scale and level shift your input signal as shown in the attached example. This requires that you have a small negative supply, such as that which can be generated with the lm7705, in order to not violate the input common-mode limitations of the op amp. Otherwise, you will need to do this scaling with multiple stages.

XTR111 +-10mV.TSC

XTR111_Block_Diagram.pptxDear Zak Kaye

Thanks for your quick response.

I have explain the purpose.

First, I have received from torque sensor(from -10mV to +10mV)

torque sensor: If it move to left then output level is negative(-10mV ~ 0V)

              If it move to right then output level is positive(0 ~ 10mV)

Second, I have send to CPU (4mA ~ 20mA level

for example, -10mV --> 4mA

              0V  --> 10mA

            +10mV --> 20mA

I have attached file as block diagram,

Please check to the component and block diagram

Thnaks and BR

PJ

PJ,

As mentioned above since you have a negative supply the presented solution sounds like it will work for you, though I would suggest using a device with lower offset voltage if you are going to run in high gain. You just need to scale the input offset and gain accordingly to generate a 4mA level with -10mV in. You could also scale for a 200mV to 1V range or something similar to run in lower gain, but I would suggest driving the XTR with a signal larger than 20mV as the offset voltage of the XTR111 itself can be as high as 1.5mV. In addition, the lower the input voltage, the smaller the Rset resistor must be and this makes you more susceptible to parasitic resistance between Rset and ground.

XTR111 1Vin.TSCHere is an example scaled to 1V in with the 4mA offset:

Dear All

Thanks for your cooperation.

I have check more detailed the circuit.
so I have changed from LF412 to INA828.
I send to ppt file for block diagram and question.
Please check to the file and inform to me.

Thanks and BRXTR111_Block_Diagram_0614.pptx

PJ

Dear all

Could you send to me the pspice lib. file about XTR111 and INA828?

Thanks and BR
PJ

Hi PJ,

We do not have a pspice model for the XTR111, but if you simulate in TINA you can use the behavioral model I provided above. The INA828 model can be found on the tools and software page for the INA828 located here: www.ti.com/.../toolssoftware

If you're using an INA to do your gain and level shifting then you should set your gain to 250 and provide a reference voltage of 2.5V to get an output of 0 to 5V for your XTR. Or if you wanted to have -10mV correspond to 4mA out then you should set your INA in a gain of 200 with Vref = 3V.

Dear Zak Kaye

Thanks for your cooperation.

Concering torque sensor circuit, I will send to you about pdf file(circuit diagram)

Please check to the circuit and advise to me.

* Circiut operation  :

 -. Input : torque sense input(+10mV ~ -10mV)

 -. Output : 4mA ~ 20mA

Thanks and BR

PJTORQUE_SENSOR_CIRCUIT_0619.pdf

Hey PJ,

I don't see exactly how you are generating the 4mA with a 5V offset on the INA. The largest gain you will have is 99V/V on the INA meaning the minimum output voltage is going to be 4V (-10mV * 99 + 5V). Assuming the connection to Vreg is a 4:1 resistive divider then you will have 4.2V at the XTR input for -10mV at the torque sensor. It looks like your span is configured for 20mA to 26mA.

Another thing I would mention is I don't think you really need a potentiometer for both the gain of the INA and the Rset resistance. Since the equation is Iout = 10*Vin/Rset, being able to manipulate one of these parameters should allow you to adjust the span accordingly.