Basic parts of analog multi-tester and definitions???TNX a lot!?

Question

Basic parts of analog multi-tester and definitions???TNX a lot!?

Answer 1

Components:

1. A 0 to 50 uA D'Arsonval meter movement, with printed scales for current, voltage, and resistance.

2. A multi-section rotary switch

3. Various high value precision resistors for the voltage dividers

4. Various low value high power precision shunt resistors for the current measurements

5. A battery (9V or 22.5V) to provide current for the resistance measurements.

For current measurements, current is routed from the positive test lead through the switch (set to whatever scale of Amps is to be measured), and through the meter in parallel with whatever shunt resistor has been switched in, finally out the negative test lead.

For voltage measurements, voltage is applied to the test leads positive and negative, and that voltage is impressed on a high resistance voltage divider (resistors), whose voltage division ratio is selected by the rotary switch.  The small divided voltage is applied directly to the meter causing it to move in proportion to the divided voltage.  For AC voltages, diodes are used to rectify the AC.  A filter can be applied to approximate an RMS voltage assuming the input is a sine-wave and it is in a range of low frequencies.

For resistance measurements, the battery is switched in series with the meter and the resistor to be measured.   In addition, the rotary switch selects other series resistors to limit the current.  This way, several decades of resistances may be measured.

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