How to measure camera current draw using a Multimeter.

Issue

It is often necessary to know how to measure current using a multimeter. Current measurements are easy to make, but they are done in a slightly different way to the way in which voltage and other measurements are made. However current measurements often need to be made to find out whether a circuit is operating correctly, or to discover other facts associated with its current consumption.

Product Line

Pelco Cameras

Environment

All Pelco Cameras -  all models and versions.

Cause

Testing, Installation, and Maintenance

Resolution

Current consists of a flow of electrons around a circuit, and it is necessary to be able to monitor the overall flow of electrons. When using a multimeter to measure current, the only way that can be used to detect the level of current flowing is to break into the circuit so that the current passes through the meter. Although this can be difficult at times, it is the best option. A typical current measurement can be made as shown below. From this it can be seen that the circuit in which the current is flowing has to be broken and the multimeter inserted into the circuit.

 

How to measure current with an analogue multimeter

It is quite easy to use an analogue meter to measure electrical current. There are a few minor differences in way that current measurements are made, but the same basic principles are used. When using the meter it is possible to follow a number of simple steps:

  1. Insert the probes into the correct connections - this is required because there may be a number of different connections that can be used. Be sure to get the right connections as there may be separate connections for very low or very high current ranges.
  2. Set switch to the correct measurement type (i.e. to measure current) and range for the measurement to be made. When selecting the range, ensure that the maximum for the particular range chosen is above that anticipated. The range on the multimeter can be reduced later if necessary. However by selecting a range that is too high, it prevents the meter being overloaded and any possible damage to the movement of the meter itself.
  3. When taking the reading, optimise the range for the best reading. If possible adjust it so that the maximum deflection of the meter can be gained. In this way the most accurate reading will be gained.
  4. Once the reading is complete, it is a wise precaution to place the probes into the voltage measurement sockets and turn the range to maximum voltage position. In this way if the meter is accidentally connected without thought for the range to be used, there is little chance of damage to the meter. This may not be true if it left set for a current reading, and the meter is accidentally connected across a high voltage point!

How to measure current with a digital multimeter

To measure current with a digital multimeter it is possible to follow a few simple steps:

  1. Turn the meter on
  2. Insert the probes into the correct connections - in many meters there are a number of different connections for the probes. Often one labeled common into which the black probe is normally placed. The other probe should be entered into the correct socket for the current measurement to be made. Sometimes there is a special connection for current measurements, and sometimes a separate one for either low or high current measurements. Select the correct one for the current measurement to be made.
  3. Set main selector switch on the meter switch to the correct measurement type, (i.e. current) and range for the measurement to be made. When selecting the range, ensure that the maximum range is above the expected reading anticipated. The range on the DMM can then be reduced as necessary. However by selecting a range that is too high, it prevents the meter being overloaded.
  4. When the measuring the current, optimise the range for the best reading. If possible enable all the leading digits to not read zero, and in this way the greatest number of significant digits can be read.
  5. Once the reading is complete, it is a wise precaution to place the probes into the voltage measurement sockets and turn the range to maximum voltage. In this way if the meter is accidentally connected without thought for the range used, there is little chance of damage to the meter. This may not be true if it left set for a current reading, and the meter is accidentally connected across a high voltage point!