wiki - Changes

Yesterday

Agilent GPIB edited ... Agilent GPIB Installation of Agilent IO Suite installs a driver that may interfere with the...

alanhume

8:51 am

Understanding the Diagnostic Report edited ... If you are unable to identify the problem, the diagnostic report may be sent to the...

MvB

7:51 am

Agilent GPIB edited ... Agilent GPIB Installation of Agilent IO Suite installs a driver that may interfere with the...

MvB

7:50 am

Friday, March 5

Minimum Switching Capacity IN EMR Relays edited ... Underlying materials or materials which resist contact erosion more effectively than gold...

davidowen

5:58 am

Relay Reliability edited ... Finding Relay failures Find out about the merits of self test, diagnostic and relay...

davidowen

3:19 am

Minimum Switching Capacity IN EMR Relays edited

davidowen

3:13 am

Minimum Switching Capacity IN EMR Relays edited Minimum Switch Capacity EMR relays often have a minimum switch capacity and Pickering...

Minimum Switch Capacity
EMR relays often have a minimum switch capacity and Pickering Interfaces generally publish this information on their data sheets for switching products. Here is an explanation of the cause and the effect on users.
EMR versus Reed Relay
The minimum capacity issue is generally confined to relays which do not have a hermetic seal, as reed relays have a hermetic seal around the contacts minimum capacity is not an issue which is seen with reed relays.
Minimum Capacity Cause
Relay contacts are generally made from selective use of precious metals. These metals have different characteristics. Gold is usually considered to be a soft metal suited to low level switching that does not tarnish with time. It is also soft, so when two contacts come together they tend to make good electrical contact under all signal conditions. However, under higher signal levels there is an increased risk of welding occurring or of contact erosion (especially DC switching where metal transfer is a significant problem) which exposes the underlying metals on the contact. So gold generally makes a good contact material for low level signals but a poor material for higher signal levels.
Underlying materials or materials which resist contact erosion more effectively than gold are more prone to surface oxidization (or other contaminants) which either do not conduct well or do not conduct at all at low signal levels.At high signal levels there is sufficient energy in the signal to punch through the surface layers and provide a good electrical contact.
As a consequence higher power relays have a very variable low power contact resistance - the behavior being dependent on how the relay is used, how many high level switching operations have been performed, the degree of hermeticity in the package and the pollutants (from outside or from the package) that are present.
Consequently the relay may have a minimum capacity for switching, for levels below the this signal the contact resistant may be higher and in some cases even an open circuit. If a relay is used in a benign environment and does not suffer significant contact erosion it may be able to handle low level signals for many years with no problems. If a relay is to be used for both high and low signal levels it may be essential to handle the signal in a different way with two relays to ensure good operation, as for example Pickering Interfaces do with the 40-194.
Caution on DMM Use
Many DMM's measure resistance with relatively low voltage and low current (1mA is common). This can cause measurement problems on relays with a minimum capacity since the DMM may show a high or even open contact when the relay is performing to specification. If the user suspects this is the case a few hot signal switches (or even dry switch operation that rely on the wiping action of the contacts to clean them) may eliminate the problem.
Return to Pickering Interfaces web site www.pickeringtest.com

davidowen

3:13 am

Sunday, February 21

Potentiometer Simulation edited ... {potentiometer.jpg} Emulation of the potentiometer requires the use of two separate...

keithmoore

3:08 pm

Friday, February 19

Cable Testing in Airframe edited ... The entire system was implemented in 6U of rack space. The system could be implemented using...

davidowen

8:58 am

60-310_800x2.jpg uploaded

davidowen

8:57 am

LXI Success Stories edited ... Large Avionics Matrix Streamlines Test A 60-552 was chosen to streamline the test systems...

davidowen

8:27 am

Cable Testing in Airframe edited Title Cable Testing in Airframe Customer :Aviation Aviation Application for ......

davidowen

8:23 am

Cable Testing in Airframe edited Title Customer :Aviation Application for Systems Integrator in France Application : After a...

Title
Customer :Aviation Application for Systems Integrator in France
Application :
After a specified number (thousands) of flying hours, every airplane, be it private or commercial, has to be dismantled and fully checked to ensure it continues to be airworthy. A commercial airplane company required a switching system that would provide the ability to test for continuity and insulation integrity of cables in the entire aircraft. Insulation tests needed to be performed to 1kV. The switching system used for the test had support cold switching at 1kV and also be suitable for use with small voltages consistent with continuity testing. The switching system needed to be an 800x2, 2 pole matrix.
Problem:
The first approach was based on GPIB backplane chassis with several switch cards using high voltage Reed Relays. This solution was too much expensive and occupied more than 18U of rack space.
There was a solution based on the use of PXI modules. The PXI solution required 4 chassis since 52 PXI cards were required, the 4 chassis needing around the same rack space as a GPIB solution. The end cost of the PXI solution was also prohibitive.
Solution:
Pickering Interfaces proposed an LXI solution to reduce both the cost and space required. The application required a great number of crosspoint switches and LXI solutions are much more effective at implementing these large matrix systems because of the lack of restrictions of the mechanical aspects when compared to modular solutions. With no LXI solution in the market, Pickering Interfaces decided to develop a standard product (Released as the 60-310) for this type of application. A 2U box with 3 density options at 100x2, 200x2 to 300x2, each with 2 poles, was developed.
The entire system was implemented in 6U of rack space. The system could be implemented using just three 2U LXI Devices to construct a 800x2 2 pole matrix with simple and cost-effective inter-Device cabling to link the products..
This solution was 30% cheaper than the alternative approaches and occupied just one third of the space of alternative approaches.
Return to Pickering Interfaces web site www.pickeringtest.com

davidowen

8:22 am

Thursday, February 18

Software Topics edited ... PXI Chassis Identification Identifying a Pickering PXI Chassis in MAX ... Switches with...

alanhume

1:46 am

Wednesday, February 17

Flexible Matrix for Avionics edited

davidowen

6:26 am

Flexible Matrix for Avionics edited ... Each test system’s switching network was made configurable out of many 75x4 high voltage...

davidowen

6:25 am

60_311_success_story_1.jpg uploaded

davidowen

6:22 am

60_311_success_story.jpg uploaded

davidowen

6:17 am

Hardware Topics edited ... BRIC A Versions Understand how the A versions of BRIC's differ from the older versions...

davidowen

3:36 am

Increasing the current from 41-740 or 41-742 PSU edited ... Further channels can be added to increase the output current capability. Adding channels in...

davidowen

3:29 am