Potentiometers – Linear and Rotary Resistive Transducers
Application Notes
Wiring and sensor setup
• This connection is typical for potentiometers and is also the connection for internally signal conditioned three‐wire sensors, typically centered at 2.5V and full scale outputs of 0.5V‐4.5V outputs. • Refer to the table on the following page for specific instructions relating to your DTS hardware
• A gain of 1.0 will be typical in the sensor settings when the desired range is the sensors full scale
• TDAS Pro and SLICEWare (v1.06x) will “flag” the range of the sensor. This is due to the expectation of a bi‐polar sensor. Your software will reflect a maximum range of ~half the requested output range. This is expected. The full range of the sensor is not affected. The linear or rotary potentiometer a uni‐polar output.
• Bench check the sensor to ensure you do not clip the signal.
• Completing the bridge externally improves the compatibility of the sensor wiring with all DAS
• Consult your documentation for the corresponding pin numbers of the sensor input connectors
• Ensure the active signal lead is connected to SIG‐. By default, DTS products complete the internal bridge on the SIG+ input when half‐bridge mode is selected (G5 does not use true bridge completion, see table on following page).
• Connect the sensors shield to the appropriate ground connection. A shield ground (case when available) is required at the DAS for low level (mV output) transducers.
• You may shunt check the sensor when using half‐bridge mode by entering the correct resistance values of 1kΩ for TDAS Pro SIM and 3kΩ for SLICE Bridge in your sensor setup
• Good practice is to set the HIGH/LOW offset limits in your sensor setup to values that are near the expected starting output of the sensor. This is especially true for ATD applications
• Do not “remove offset” in your sensor setup
SAMPLE
SENSOR
FILES
DAS
Potentiometer, 3‐Wire Half‐Bridge
Excitation Source
Rotary, String or Cable Potentiometer
*
EXC+
Half‐bridge switch
EXC‐
SIG+
*
Amplifier
SIG‐
Positive Direction
GND
ID‐
ID+
EID Interface
* Bridge completion: TDAS Pro SIM=1kΩ SLICE Bridge=3KΩ
8/11/2014
Potentiometers – Linear and Rotary Resistive Transducers
DTS Specific Data Acquisition System Notes
• Please note the specific requirements of your system
• If you need specific connector information, please refer to your owners manual. If additional information is needed, provide a DTS hardware serial number when contacting support
• Always provide the make and model of your sensor and include a sensor datasheet when available
Product Family
SLICE Nano/Micro
Input Range Limitations
Half‐bridge sensor setting
0.1V to 4.9V. Signals near the start Switches 3kΩ hardware bridge and end of pot travel will not read completion onto the SIG+ line
correctly
Software Notes
SLICEWare does not correctly display the maximum range selected. Software assumes bipolar on a unipolar sensor. Range error is false
SLICE Pro
0.1V to 4.9V up to 45kHz Switches 3kΩ hardware bridge bandwidth. Signals near the start completion onto the SIG+ line
and end of pot travel will not read correctly
SLICEWare does not correctly display the maximum range selected. Software assumes bipolar on a unipolar sensor. Range error is false
TDAS Pro SIM
No limitations with any excitation
TDAS Control does not correctly display the maximum range selected. Software assumes bipolar on a unipolar sensor. Range error is false
TDAS G5
0.5V to 4.5V. Signals near the start G5 applies 2.5V reference to SIG‐ and end of pot travel will not read line. DTS recommends the bridge is completed with external resistors. correctly
Not critical with high output sensors. 8/11/2014
Switches 1kΩ hardware bridge completion onto the SIG+ line
TDAS Control does not correctly display the maximum range selected. Software assumes bipolar on a unipolar sensor. Range error is false
SAMPLE
SENSOR
FILES
Potentiometers – Linear and Rotary Resistive Transducers
Alternate Wiring: Series Resistors
• Series resistance on each excitation lead decreases the output which, reduces the sensors output at full scale to well within the DAS input range
• Use the potentiometers Rt value as an approximate choice for resistors R1 and R2. This method will reduce the output by 1/3. Recalibrate or recalculate sensitivity
• Use half‐bridge mode in your software/hardware
• Offset may be removed
SAMPLE
SENSOR
FILES
Potentiometer, Reduced Output,
3‐Wire Half‐Bridge
Rotary, String or Cable Potentiometer
R1
EXC+
EXC‐
R2
SIG+
SIG‐
Positive Direction
GND
ID‐
ID+
8/11/2014