Read Microsoft Word - Make_Your_Own_DC-Current_Shunt_Meter.doc text version

How To Make A DC-Current Shunt for a Digital or Analog Meter

(5/7/2007)

AWG gauge OOOO OOO OO 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 Metric 2.0 33 Metric 1.8 34 Metric 1.6 35 Metric 1.4 36

Diamet er Inches 0.4600 0.4096 0.3648 0.3249 0.2893 0.2576 0.2294 0.2043 0.1819 0.1620 0.1443 0.1285 0.1144 0.1019 0.0907 0.0808 0.0720 0.0641 0.0571 0.0508 0.0453 0.0403 0.0359 0.0320 0.0285 0.0254 0.0226 0.0201 0.0179 0.0159 0.0142 0.0126 0.0113 0.0100 0.0089 0.0080 0.0079 0.0071 0.0071 0.0063 0.0063 0.0056 0.0055 0.0050

Diameter mm 11.6840 10.4038 9.2659 8.2525 7.3482 6.5430 5.8268 5.1892 4.6203 4.1148 3.6652 3.2639 2.9058 2.5883 2.3038 2.0523 1.8288 1.6281 1.4503 1.2903 1.1506 1.0236 0.9119 0.8128 0.7239 0.6452 0.5740 0.5105 0.4547 0.4039 0.3607 0.3200 0.2870 0.2540 0.2261 0.2032 0.2000 0.1803 0.1800 0.1600 0.1600 0.1422 0.1400 0.1270

Ohms per 1000 ft 0.0490 0.0618 0.0779 0.0983 0.1239 0.1563 0.1970 0.2485 0.3133 0.3951 0.4982 0.6282 0.7921 0.9989 1.2600 1.5880 2.0030 2.525 3.184 4.016 5.064 6.385 8.051 10.150 12.800 16.140 20.360 25.670 32.37 40.81 51.47 64.90 81.83 103.20 130.10 164.10 169.39 206.90 207.50 260.90 260.90 329.0 339.0 414.8

Ohms per km 0.1607 0.2027 0.2555 0.3224 0.4064 0.5127 0.6462 0.8151 1.0276 1.2959 1.6341 2.0605 2.5981 3.2764 4.1328 5.2086 6.5698 8.282 10.444 13.172 16.610 20.943 26.407 33.292 41.984 52.939 66.781 84.198 106.17 133.86 168.82 212.87 268.40 338.50 426.73 538.25 555.61 678.63 680.55 855.75 855.75 1079.1 1114.0 1360.0

Maxim um amps for chassis wiring 380 328 283 245 211 181 158 135 118 101 89 73 64 55 47 41 35 32 28 22 19 16 14 11 9 7 4.7 3.5 2.7 2.2 1.7 1.4 1.2 0.86 0.7 0.53 0.51 0.43 0.43 0.33 0.33 0.27 0.26 0.21

Maxim um amps for power transmi ssion 302 239 190 150 119 94 75 60 47 37 30 24 19 15 12 9.3 7.4 5.9 4.7 3.7 2.9 2.3 1.8 1.5 1.2 0.92 0.729 0.577 0.457 0.361 0.288 0.226 0.182 0.142 0.113 0.091 0.088 0.072 0.072 0.056 0.056 0.044 0.043 0.035

Shunt length in Inches for 1 mv = 1 amp 244.898 194.175 154.044 122.075 96.852 76.775 60.914 48.290 38.302 30.372 24.087 19.102 15.150 12.013 9.524 7.557 5.991 4.752 3.769 2.988 2.370 1.879 1.490 1.182 0.938 0.743 0.589 0.467 0.371 0.294 0.233 0.185 0.147 0.116 0.092 0.073 0.071 0.058 0.058 0.046 0.046 0.036 0.035 0.029

Shunt length in CM for 1 mv = 1 amp 622.200 493.330 391.371 310.151 246.068 195.060 154.760 122.687 97.312 77.165 61.196 48.532 38.490 30.521 24.197 19.199 15.221 12.074 9.575 7.592 6.020 4.775 3.787 3.004 2.382 1.889 1.497 1.188 0.942 0.747 0.592 0.470 0.373 0.295 0.234 0.186 0.180 0.147 0.147 0.117 0.117 0.093 0.090 0.074

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How To Make A DC-Current Shunt for a Digital or Analog Meter

(5/7/2007)

Metric1.25 37 Metric1.12 38 Metric 1 39 40

0.0049 0.0045 0.0044 0.0040 0.0039 0.0035 0.0031

0.1250 0.1143 0.1120 0.1016 0.1000 0.0889 0.0787

428.2 523.1 533.8 659.6 670.2 831.8 1049.0

1404.0 1715.0 1750.0 2163.0 2198.0 2728.0 3440.0

0.2 0.17 0.163 0.13 0.126 0.11 0.09

0.034 0.0289 0.0277 0.0228 0.0225 0.0175 0.0137

0.028 0.023 0.022 0.018 0.018 0.014 0.011

0.071 0.058 0.057 0.046 0.045 0.037 0.029

The "Shunt Length" column in the above table can be used to determine the length of cable to be used to make a heavy duty DC amp meter. The way the result works is one measures the voltage drop across a given length of the cable that is currently in use supplying the 12 volts from the battery. This voltage drop is measure ideally by use of a digital meter; however an analog meter can also be used. One mili-volt measured is equal to one amp of current. Harbor Fright tools digital meter item 90899 or equivalent can be used. These are on sale at times in the store for as low as $2.99 see http://www.harborfreight.com/ 90899-2VGA Cen-Tech 7 FUNCTION MULTI-TESTER $9.99 $4.99

If this meter is used on the 200 mv scale then one can read in tenths of an amp up to 200 amps. For small wire sizes if one uses 10 times the length as shown in the table above then the readings will be down to one hundredth of an amp. One simply clips, solders, or clamps the volt meter leads onto the proper length of existing 12 volt supply cable.

Shunt Wire Length

12 V

If an analog meter is used that is close to 1 ma full scale (meter movement about 81 ohms) and planned to be used to measure 20 amps full scale instead of a digital meter, then multiply the length found above by a factor of 4. For other configurations see: http://www.uoguelph.ca/~antoon/gadgets/shunts/shunts.html Load Carrying Capacities (see table above) The chart is a guideline of ampacity or copper wire current carrying capacity following the Handbook of Electronic Tables and Formulas for American Wire Gauge. As you might guess, the rated ampacities are just a rule of thumb. In careful engineering the insulation temperature limit, thickness, thermal conductivity, and air convection and temperature should all be taken into account. The Maximum Amps for Power Transmission uses the 700 circular mils per amp rule, which is very very conservative. The Maximum Amps for Chassis Wiring is also a conservative rating, but is meant for wiring in air, and not in a bundle. For short lengths of wire, such as is used in battery packs you should trade off the resistance and load with size, weight, and flexibility. See: http://www.powerstream.com/Wire_Size.htm This table is quite useful to print out and use as a reference.

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Microsoft Word - Make_Your_Own_DC-Current_Shunt_Meter.doc