• Load Meter Testing

  • General discussion about locomotives, rolling stock, and equipment
General discussion about locomotives, rolling stock, and equipment

Moderator: John_Perkowski

  by WP Mechanic
Just wondering how others comply with FRA regs in their annual testing of locomotive ammeters. I've thought of making my own voltage source with volt meter, and then doing the math to compare it to the ammeter reading. Any other methods?
  by WVU
We have Load Meter Testers that our Electricians use for testing the Load Meters. Another way I check Load Meters if they don't seem correct is I hook a digital Volt Meter to them on the back of the load meter and set it on the 200 Millivolt Scale. The Shunt on the older EMD Units is a 1000 Amp 50 Millivolt Shunt for feeding the Load Amp Meter. With this Shunt being 1000 Amp 50 Millivolt your multiplier is 20 for how ever many millivolts you are recording and it should match your Load Meter in Motoring or in Dynamic Braking. Let's say you have your doubt's about the 1000 Amp 50 Millivolt Traction Motor Shunt feeding the Load Meter. You can then compare it against your 4000 Amp 50 Millivolt Main Generator Shunt. Your Multiplier/Divider for the 4000 Amp/50 Millivolt Main Generator Shunt is 80. If you are on a 4 Axle Unit that is a Full Parallel Unit (No Transition) for what ever Throttle Notch in Motoring you are in record your Main Generator Output Amps (which will be in millivolts on the 200 Millivolt Scale and times it by 80 and what ever it is, then divide it by 4 and it should match your Load Meter( 4 Traction Motors in Parallel). Now if you are on a SD40-2 and if you have not made Transition you would record the Main Generator Shunt Readings and Divide it by 3 (for 3 sets of two traction motors working together) and it should match your Load Meter. If you are on that same SD40-2 and it has made Transition, you would divide your Main Generator Shunt Reading by 6 because you are in Full Parallel.