Pickering Interfaces' Blog - Insights into Switching Technology

What is a Programmable Resistor?

Posted by Kim Otte on Aug 25, 2014 3:13:00 PM

programmable resistor is designed to emulate the use of resistive sensors and variable resistors in systems when testing devices such as engine controllers.

programmable-resistor-chain
Resistor chain used in a typical programmable resistor

In their simplest form, Pickering's programmable resistors consist of a basic chain of resistance values switched in or out of circuit with reed relays, electro-mechanical relays or solid state switches. We also offer multi-channel programmable resistors with very fine value adjustment and high accuracy including programmable resistive bridges for strain gauge simulation.

two-channel-programmable-resistor
Two channel precision programmable resistor with calibration facility

Applications for Programmable Resistors 

Programmable resistors have many applications in automated test, verification and simulation systems: 

  • Strain Gauge Simulation
    • Used in mechanical systems to measure the tension or compression of structural components. Simulation requires extremely fine setting resolution with high accuracy and temperature stability. 
      strain-gauge-simulator-diagram
Strain Gauge Simulator with six channels and calibration facility
  • Temperature Sensor Simulation
    • Simulation of resistance based temperature sensors such as positive or negative temperature coefficient thermistors. 
    • Resistance Temperature Detectors (RTDs) can be wire-wound or thin film. Both PT100 and PT1000 types can be simulated, requiring fine setting resolution. 
  • Pressure Sensor Simulation 
    • For the simulation of pressure senders in mechanical systems or barometric pressure sensors in applications such as altimeters in the aerospace industry. 
  • Select on Test Resistance 
    • A programmable resistor can be used in a test environment where a component's value is optimized at the production test stage. 
  • Load Resistor 
    • Where a circuit under test requires the connection of an external load. 
  • Position Sensor Simulation 
    • Rotary or linear position sensors in mechanical systems usually take the form of potentiometers and are used in applications such as throttle position senders in automotive systems. 
  • Switch Simulation 
    • Can be used to simulate the contacts of a worn or contaminated switch for automotive ECU (Engine Control Unit) testing. 
  • Fault Insertion 
    • Can be used for injecting fault conditions when testing the fault tolerance of aircraft or automotive control systems. 

Selecting a Programmable Resistor

Pickering offers a variety of PXI programmable resistor modules and PCI programmable resistor cards for use in medical, automotive and aerospace applications. We offer different features for use in different applications, these include:

  • Platform
    • Solutions in both the PXI and PCI formats
    • Ethernet control of any of our PXI modules when installed in our LXI Chassis
  • Number of Channels
    • Between 1 and 18 channels
  • Range
    • Many resistance ranges are available with values from a short circuit to millions of Ohms
    • Modules and cards are available with a narrow setting range and very fine resolution for simulating sensors and strain gauges
  • Resolution
    • Resistance setting resolutions are available from 10Ω to 2mΩ for a wide range of applications
  • Power Handling
    • Generally 100mW for precision programmable resistors and up to 1W for standard programmable resistors
    • We also offer a PXI programmable load module with up to 15W power handling (model 40-292)
  • Minimum Resistance Value
    • The lower the minimum resistance value required the greater the errors caused by relay contact resistance and copper trace losses.
    • Generally, modules and cards with a low minimum resistance do not have as wide a range of resistance values as those with higher minimum resistances.
  • Accuracy
    • High accuracy requires careful design to ensure low loss paths, management of thermoelectric EMF and the use of higher stability resistors
  • Calibration Port
    • A calibration port allows the user to check the resistor channel without having to disconnect the front panel connector. It can be used to connect any of the resistor channels to a DMM to perform an accurate four terminal measurement.
  • Custom Programmable Resistors

pickering-programmable-resistorsOur entire range use real resistors, they do not use current loads or other electronic means to control the resistance value. Therefore they behave in exactly the same way as an actual resistor.

We carry over 130 PXI modules and over 120 PCI cards featuring:

  • Up to 18 channels in a single PXI/PCI slot
  • Resistance ranges from 1Ω to 22MΩ
  • Resolutions down to 2mΩ with accuracies down to 0.03%
  • PXI modules can be supported in our LXI Chassis
  • Supported by a full range of connector and cabling solutions

You can also learn more about programmable resistors on our knowledgebase, feel free to contact one of our simulation engineers for more information or...

   Webinar: Using Programmable Resistors for Sensor Simulation  Video: Intro to Programmable Resistors 

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Topics: test and measurement systems, Programmable Resistor, pxi simulation, pci simulation, sensor simulation in test