Problem of LFH200DSUB50X4S for Switch 2575

[faili]

I used the LFH200 cable(LFH200DSUB50X4S) to connect the PXI-2575 and measured the

high resistance. Recently I find that a high resistance can be measured in some channel

of LFH200 when LFH200 doesn't connect to any resistance.

So I had such test:

1. Connect the LFH200 to PXI2575, and connect the J3 of  LFH200 to FLK-D50 SUB/S.

The channels don't connection anything.

2. Connect the DMM4071 to the 23Pin and 24Pin of FLK-D50. Use the NI-SWITCH Soft Front

Panel to change the channel from 0 to 98. The topology is 98*1 2 wire. Use DMM4071 to

measure the resistance between the CH+ and CH- of each channel. The scale of DMM4071

is 5G.

3. The result is the resistance between most of channels can not be measured by DMM4071.

But the resistance between the channels in J2 can be measured. The value of resistace is from

1.15G to 5G. Different channel has different resistance. And I find the value will change with the

temperature of the environmental. When the temperature is raised, the resistance is also raised.

Such as when temperature is 25.8C, the value is 3G. When temperature is 28C, the value is 4.7G.

Because I used the PXI2575 to measure the resistance, if there is resistance between the channels,

It will have a great effect on my measurement.

I think the isolation resistance between the CH+ and CH- of the channel must be great than 100G.

Is there problem in the LFH200 cable?

[chericks1]

Hi faili,

Thank you for troubleshooting this issue in detail.  Are you still investigating this issue?  Please let me know!

Chad Erickson
Switch Product Support Engineer
NI - USA

[faili]

Hi Erickson

    The agent of NI promise me to change the cable.

But I don't whether the new one is ok.

I think it is better to find the reason and look for

the solution to avoid the problem. Can you help me?

Thanks a lot!

                                                           Faili