Measurements and Connections

Voltage measurement





A voltmeter is connected in parallel with the test component.
Connect + to + and - to -.

Current measurement





An ammeter is connected in series with the test component. Connect the positive terminal on the instrument to the point with the highest potential. Where the current is likely to be high, a shunt should be connected in series with the test component to prevent damage to the instrument. The ammeter is connected to the shunt.





The ammeter and shunt are often matched so that the true value of current is obtained by multiplying the indicated reading by a specified shunt factor.





A clip-on ammeter may be used instead of a shunt. However, this type may not be used to measure a.c. current in uninsulated leads or in the vicinity of equipment generating a strong magnetic field.

Resistance measurement





Disconnect other leads connected to the test component to ensure that other current sources cannot affect the reading. If the connections are good, the instrument will indicate 0 ohm. For an open-circuit, the reading will be infinity. Since the instrument has a built-in battery, it must be calibrated to compensate for battery condition. (See instrument / ohm meter instructions.)

Maintenance
Use known resistances to check the instrument readings at least once per month, or if the instrument is suspected to be reading incorrectly. Ensure that the instrument is stored away from strong heat, shocks, impact and high humidity.

Instrument housings are often made of plastic for durability and toughness.
However, this means that the housing may acquire a static charge if cleaned with a dry cloth, causing inaccurate readings. To prevent this, always clean the instrument with a slightly moistened cloth. Never replace instrument fuses with car fuses. See the instrument manufacturer's instructions for other information on specifications, operation, maintenance etc.