We offer a variety of resistor modules with different features which make them attractive for different applications.
As with most products resistor modules are designed with a number of constraints:
- Platform - we offer solutions in both the PXI and PCI formats
- Number of channels - the greater the number channels the lower the cost per channel, but the range and/or resolution
of each channel may be more restricted.
- Range - as the range of the module is extended it needs more components, reducing range restricts the number of applications
that can be served by a channel
- Resolution - increasing resolution requires more components, degrading resolution decreases make it harder to achieve
the required resistance value harder
- Speed - faster operation can help reduce test time and reduce the duration of transients as the resistor state is changed
transient resistance values
- Power handling - the greater the power the resistor channel has to handle the bigger the components used have to be.
Dissipation of high powers may impact component stability
- Minimum resistance value - The lower the minimum resistance value required the greater the errors caused by relay contact
resistance and copper trace losses.
- Accuracy - high accuracy requires the use of low loss paths, management of thermoelectric EMF's and the use of higher
stability (and therefore more expensive) resistors
- Calibration Port - a calibration port allows the user the check the resistor channel without having to disconnect the
user connector form the UUT. It can be used to select any of the resistor channels and connect it to a DMM to do
an accurate 4-terminal measurement. This can help improve accuracy in the measurements and be used as a calibration
support tool. However, it takes space and reduces increases the cost of the module
The Pickering range of resistor modules all use real resistors, they do not use current loads or other electronic means to
control the resistance value. So they all behave in exactly the same way as a real resistor does.
The most common application for resistor modules is simulation of temperature dependent resistors. Information on how to
simulate platinum based sensors can be found here
including a utility program for conversion from temperature to resistance.
Pickering Interfaces Resistor Module Range
The following is a summary of the range from Pickering, the text should help you chose the best model for your application:
High performance three channel resistor module designed for wide resistance range with very fine setting resolution. Software
control is easy since it uses resistance calls (in ohms) rather than bit patterns. It includes a Calibration Port
a separate connector.
This two channel module is similar to 40-260 but has a much lower bottom end resitance value. The design is optimized for
high performance applications requiring low as well high resistance settings. It supports a separate Calibration Port
on its own connector to ensure the
best performance and uses a resistance call to set its value.
This module is designed to provide a narrow resistance range with high channel count and very high performance levels. It
is designed specifically for RTD simulation applications. It uses resistance calls which can easily be adapted by user to
turn into temperature calls corresponding to the users RTD device, a specific example can be found here Platinum Temperature Sensors
and a software utility
here PRT Utility
The 40-262 supports a separate calibration port
40-265 (PXI) and 50-265 (PCI)
Designed specifically for strain gauge simulation this module includes a bridge circuit and excitation system to allow it
to emulate a strain gauge. The resistance control range is very small and has very fine control, permitting it emulate small
strain levels. It supports a calibration port
40-297(PXI) and 50-297 (PCI)
An excellent alternative to 40-295/290 where an accuracy specification is important but not requiring the accuracy of the
precision range. The design uses EMR's. Control is by resistance calls to the module and the module works out the best setting
to achieve that resistance by use of stored calibration information in the module. The resistors fitted to 40-297 have a
low temperature coefficient which leads to an excellent accuracy and temperature stability.
40-293 (PXI) and 50-293 (PCI)
For applications requiring less performance the 40-293 offers a lower cost alternative based on EMR's and lower accuracy
resistors than 40-297. In addition to offering 2 or 4 channels the design also optionally supports 8 SPDT relays which can
be used for general purpose switching applications or used to insert additional components into the resistor chains.
40-295 (PXI) and 50-295 (PCI)
Provides a denser solution than 40-290 and is suited to applications were accuracy is not critical but speed of operation
is. It uses relay patterns for control, for new system designs we recommend using 40-297 unless speed is critical - based
on reed relays the 40-295 offers much faster operating speed than EMR solutions which may be important in real time applications.
Reed relays tend to have a higher thermo-electric EMF than EMR's, see Importance of Thermoelectric EMF in resistor simulators
and a higher contact resistance in the relay which leads to a higher residual path resistance.
40-294 (PXI) and 50-295 (PCI)
For applications requiring less performance and reed relays the 40-294 offers a lower cost alternative based on EMR's and
lower accuracy resistors. In addition to offering 2 or 4 channels the design also optionally supports 8 SPST relays which
can be used for general purpose switching applications or used to insert additional components into the resistor chains.
The 40-280 provides the user with a set of relays that allows the simple provision of fixed resistor values. Each resistor
can be set to open circuit, resistor selected or shorted out. Channels can be added in parallel so that a few different fixed
values can be offered across two connections. This module is a good choice where you simply need to have a few fixed values
rather than a variable resistor. The resistors can either be fitted by the user (standard configuration) or Pickering Interfaces
can offer a facility to load the required resistors.
Provides a simple variable resistor based on the use of a binary chain of resistors controlled by reed relays. It is controlled
using relay patterns to set the resistance value, but has no claimed overall accuracy. It is bested suited for low cost dense
applications not requiring the best accuracy available.