maverick33
Member
Hello all,
I just have a couple of questions regarding fusing of analog inputs...
Background:
I am in the process of commissioning and testing some new equipment from Europe that uses AB Control Logix with 1756-IF16 analog input cards with pretty much everything wired single ended. The inputs also go through barriers (MTL 7087+) due to Class 1 Div 2 hazardous location requirements.
Problem:
Occasionally some of the inputs spike to maximum for no apparent reason. This seems to be isolated to temperature transmitters (4-20 mA) that all of a sudden max out for no apparent reason. Checked the sensor and wiring and everything checks out up until a small 32mA resistive (don't remember how many ohms at the moment)fuse that is just before the card input.
I have been able to resolve the problem by removing power to the barrier cards temporarily and then reapplying it. This seems to work but the problem still occurs ay completely random intervals. I had not seen this type of resistive fuses but have heard through the grape vine that these are often used with Siemens analog input cards. I don't have any Siemens experience and was wondering if anybody could confirm this?
I inquired with AB about potential problems with these fuses but they were unable to help. I removed these resistive fuses and the sensors seems to be working without any problems now but I am still just curious as to if anyone else has seen/used these before?
Thanks.
I just have a couple of questions regarding fusing of analog inputs...
Background:
I am in the process of commissioning and testing some new equipment from Europe that uses AB Control Logix with 1756-IF16 analog input cards with pretty much everything wired single ended. The inputs also go through barriers (MTL 7087+) due to Class 1 Div 2 hazardous location requirements.
Problem:
Occasionally some of the inputs spike to maximum for no apparent reason. This seems to be isolated to temperature transmitters (4-20 mA) that all of a sudden max out for no apparent reason. Checked the sensor and wiring and everything checks out up until a small 32mA resistive (don't remember how many ohms at the moment)fuse that is just before the card input.
I have been able to resolve the problem by removing power to the barrier cards temporarily and then reapplying it. This seems to work but the problem still occurs ay completely random intervals. I had not seen this type of resistive fuses but have heard through the grape vine that these are often used with Siemens analog input cards. I don't have any Siemens experience and was wondering if anybody could confirm this?
I inquired with AB about potential problems with these fuses but they were unable to help. I removed these resistive fuses and the sensors seems to be working without any problems now but I am still just curious as to if anyone else has seen/used these before?
Thanks.
