Page 8 - July 2022 Track N Times

TECHNICAL TRAINING

Tech Tip Bundle Continued

HMI. Usually, an open or shorted circuit will display a “slot fault” or “out of range” indication. From there, read-
ings taken with a multimeter can help determine where the problem is. Voltage readings across the transmitter
can vary but should be between 1-5Vdc depending on the scale of the transmitter. High voltage readings of 15-
24Vdc indicates an open circuit, low voltage readings of zero or near zero indicates a short. The relatively low
voltage readings make troubleshooting a 4-20 circuit challenging, so bear this in mind when troubleshooting. Sub-
stitution of the transmitter is a viable option if you have a new one on hand.

A conclusive troubleshooting method is to open or break
the circuit and measure the current directly. This method

involves changing the multimeter’s lead configuration to
make it part of the circuit. This method can be helpful to
confirm the input channel on the PLC card is good or bad
when other troubleshooting methods seem to indicate a
good circuit, but the readings do not agree with what is
measured. If you measure a signal of 4-20 mA and the dis-
play does not correspond, it is likely the card or channel is
faulty and will need to be replaced.

Remember to return the multimeter leads to their normal
position before going back to voltage and ohm measure-

ment.

We hope this information has been helpful, if you have
questions contact a technician, we are always glad to help!

Congratulations to the crew of RG408!

Led by Superintendent Matt Miller, Assistant Manager Rob Stewart and Manager Nick Karjalahti. A Customer
Compliment was submitted from Steve Ashmore, Union Pacific Railroad, General Director-Engineering Infrastruc-
ture. Below is what Steve submitted.
Loram Team,
I know the last year and a half or so has been a challenge for all of us. I wanted to take a minute to share a positive story
from this week.
I was able to visit the RG408 on Monday night on the Mason City, IA subdivision. Overall, my experience was very positive.

• The crew was very passionate about safety. They took a lot of pride in what they were doing.

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