Model M3-A2 Handheld Multimeter (Cat. #2508)

Advantages

• Completely solid state.
• Selectable input resistance.
• Overload protection (even on 1mV range).
• Both instruments identical, accurate, extremely rugged.
• Low maintenance costs.

Center Zero

• Right voltmeter: Taut-band instrument driven by amplifier, with 9 ranges 1mV to 10V and selectable input resistance from 1 to 200 MΩ.
• Left voltmeter: Taut-band instrument driven by amplifier, with 9 ranges 1mV to 50V; Milliammeter / ammeter with 8 ranges 1mA to 10A (20mV drop shunts). Built-in IR drop contact checking circuit.

Selectable Input Resistance

Right voltmeter: Input resistance of 1,10, 25, 50,100 & 200MΩ selectable by rotary switch. Selectable input resistance permits detection of high resistance in the external circuit and the elimination of resulting errors in nearly all cases. A very important factor in structure to earth potentials, where errors in reading can be very costly. Note: Does not function on the 1mV and 5mV ranges, which have a fixed resistance of 1000Ω.

Overload Protection

Advanced design features virtually eliminate the chance of damage to either meter from electrical overload on all volt and millivolt ranges, even the 1mV range. Tests indicate that the M3-A2 will withstand AC or DC voltages far in excess of any encountered in normal field testing. Note that the ammeter shunts are not protected by the amplifier, and are therefore subject to damage by current overloads.

Contact Checking Circuit

A built in I-R drop contact checking circuit is used to determine when good low-resistance contacts are obtained. Circuit may also be used like an ohmmeter for checking continuity of test leads.

Voltmeters with Amplifiers

• Right voltmeter: Selectable input resistance of 1, 10, 25, 50,100 & 200MΩ on ranges from 10mV through 10V. 1mV and 5mV ranges have fixed resistance of 1000Ω.
• Left voltmeter: 10MΩ input resistance on all ranges from 10mV through 50V. lmV and 5mV ranges have fixed resistance of 1000Ω.
• Solid State integrated-circuit amplifier.
• Operated by easy-to-replace penlight cells with long shelf life.
• Temperature compensated.
• Operating range 0°F to 150°F.
• Short warm up time.
• Good response time on all ranges.
• Very stable zero. No need to readjust zero when changing ranges (except for 1mV and 5mV ranges).
• AC filters rejects 60 Hz power system potentials up to 35 VAC.

Instruments

The instruments are special taut-band, high-torque type built to rigid M. C. Miller Co., Inc. specifications. The instruments are inherently more resistant to mechanical damage, and since both instruments are identical, one spare instrument can be used as a replacement for the other. Replacement instruments, if ever needed, are low in cost and readily available. Scales have clearly marked 110 divisions from end to end (0.5V to 0 to 0.5V and l.lV to 0 to 1.1V). They are 4.0″ long and are of the mirror type. Pointers are knife-edge type. Full scale and tracking accuracy is within 1 1/2% of full scale except for the 1mV and 5mV.

Shunts

Built in multi-range ammeter shunt has high overload capacity and a high degree of accuracy. Use of optional accessory external shunt extends the range of current measurements to 100 A and can be used with either meter.