I have a variable AC power supply. 0-12V 0-1800A 60hz.
I have always been told to trust the current shunts and not current clamps when measuring current. The current clamps are supposed to accurate to less then 2%. Our current clamps have always been about 5-15% different then the current shunts though. I want to know why, and which one I should believe.
My boss wants me to prove to him that the shunts are more accurate than the clamps but I don't know where to begin.
All items are calibrated annually.
- Fluke 353 (1.5% accurate)
- Ideal 61-746 (1.7% accurate)
- Current shunt 500A 50mV (10:1 ratio) (Empro)
- Current shunt 3000A 50mV (60:1 ratio) (Ram Meters)
- Current shunt 2000A 50mV (40:1 ratio) (Empro) (EDIT: Added)
mV meters for the shunts are fluke 45 and Fluke 289 both read the same
I adjusted the power supply based on the current shunts.
500A shunt - first Iteration
Shunt Fluke Ideal
Target mV Current
50 5.5 55 48 49 13% 11%
100 10.5 105 91 92 13% 12%
200 20.1 201 178 182 11% 9%
300 30.1 301 263 269 13% 11%
3000A shunt - first Iteration
Shunt Fluke Ideal
Target mV Current
100 1.716 102.96 98.3 100.3 5% 3%
200 3.345 200.7 190.7 194.7 5% 3%
300 5.023 301.38 284.8 292.1 6% 3%
400 6.695 401.7 379.4 389.1 6% 3%
500 8.356 501.36 471 484 6% 3%
500A shunt - second Iteration
Shunt Fluke Ideal
Target mV Current
50 5.125 51.25 45.3 46.5 12% 9%
100 10.304 103.04 91.9 93.5 11% 9%
200 20.3 203 181.2 185.1 11% 9%
300 30.225 302.25 269.3 275.8 11% 9%
400 40.21 402.1 357 366.2 11% 9%
2000A shunt - first Iteration (Fluke 45)
Shunt Fluke Ideal
Target mV Current
50 1.21 48.4 37.17 38 23% 21%
100 2.44 97.6 84.7 86.4 13% 11%
200 5.02 200.8 181.9 186.3 9% 7%
300 6.31 252.4 230.5 235.8 9% 7%
400 10.09 403.6 360.2 372.2 11% 8%
500 11.31 452.4 405 415 10% 8%
2000A shunt - second Iteration (Fluke 45)
Shunt Fluke Ideal
Target mV Current
50 1.26 50.4 29.33 29.5 42% 41%
100 2.48 99.2 65.7 65.5 34% 34%
200 5.14 205.6 141.3 144.1 31% 30%
300 7.46 298.4 207 211.5 31% 29%
400 9.89 395.6 284.4 290.6 28% 27%
500 12.5 500 355.3 362.6 29% 27%
2000A shunt - third Iteration (Fluke 289)
Shunt Fluke Ideal
Target mV Current
50 1.21 48.4 37.2 37.4 23% 23%
100 2.51 100.4 76.6 77.3 24% 23%
200 5.14 205.6 165.5 168.8 20% 18%
300 7.58 303.2 252.6 257.8 17% 15%
400 10.11 404.4 344.6 351.7 15% 13%
500 12.49 499.6 418 426 16% 15%
EDIT: After I calculated the error rates it looks my 500A is off more than the 3kA. I am going to try it with a 3rd shunt tomorrow.
EDIT2:
200A 50mV Shunt
Fluke 353 Clamp Meter
Fluke 45