FlexiForce user manual

02/05/09 FlexiForce Sensor User Manual (Rev G) 9
High-Temperature FlexiForce Sensors
The High-Temperature HT201 sensor is available in the following force ranges* (as tested with
the sample drive circuit
).
• Sensor HT201-L Low: 0-30lb (133N) force range
• Sensor HT201-H High: 0-100lb (445N) force range
* In order to measure forces outside specified ranges, use recommended circuit and adjust
drive voltage and/or reference resistance
APPLICATION
There are many ways to integrate the FlexiForce sensor into an application. One way is to
incorporate it into a force-to-voltage circuit. A means of calibration must then be established to
convert the output into the appropriate engineering units. Depending on the setup, an adjustment
could then be done to increase or decrease the sensitivity of the sensor.
An example circuit is shown below. In this case, it is driven by a -5 V DC excitation voltage.
This circuit uses an inverting operational amplifier arrangement to produce an analog output
based on the sensor resistance and a fixed reference resistance (R
F
). An analog-to-digital
converter can be used to change this voltage to a digital output. In this circuit, the sensitivity of
the sensor could be adjusted by changing the reference resistance (R
F
) and/or drive voltage (VT);
a lower reference resistance and/or drive voltage will make the sensor less sensitive, and increase
its active force range.
In the circuit shown, the dynamic force range of the sensor can be adjusted by
changing the reference resistor (R
F
) or by changing the Drive Voltage (V
O
). Refer to
the Saturation
section for additional information.