AEMC JM840A Operating Manual

AC Current Probe
Model JM840A

User Manual

DESCRIPTION

The JM840A (Catalog # 2110.85) is designed for use in industrial environments. The “squared” jaws
permit multiple conductor or bus bar positioning. The current output makes it the perfect tool for
measurement with DMMs, recorders, power and harmonic meters. The Model JM840A is compatible with
any AC ammeter, multimeter, or other current measuring instrument with an input impedance lower than
5Ω. To achieve the stated accuracy, use the JM840A with an ammeter having an accuracy of 0.75%.

WARNING

These safety warnings are provided to ensure the safety of personnel and proper operation of the
instrument.

• Read the instruction manual completely and follow all the safety information before attempting
to use or service this instrument.

• Use caution on any circuit: Potentially high voltages and currents may be present and may
pose a shock hazard.

• Read the Safety Specifications section prior to using the current probe. Never exceed the
maximum voltage ratings given.

• Safety is the responsibility of the operator.

• ALWAYS connect the current probe to the display device before clamping the probe onto the
sample being tested.

• ALWAYS inspect the instrument, probe, probe cable, and output terminals prior to use.
Replace any defective parts immediately.

• NEVER use the current probe on electrical conductors rated above 600 V in overvoltage
category III (CAT III). Use extreme caution when clamping around bare conductors or bus bars.

INTERNATIONAL ELECTRICAL SYMBOLS

This symbol signifies that the current probe is protected by double or reinforced insulation. Use
only factory specified replacement parts when servicing the instrument.

This symbol signifies CAUTION! and requests that the user refer to the user manual before
using the instrument.

This is a type A current sensor. This symbol signifies that application around and removal
from HAZARDOUS LIVE conductors is permitted.

DEFINITION OF MEASUREMENT CATEGORIES
Cat. I: For measurements on circuits not directly connected to the AC supply wall outlet such as

protected secondaries, signal level, and limited energy circuits.

Cat. II: For measurements performed on circuits directly connected to the electrical distribution system.

Examples are measurements on household appliances or portable tools.

Cat. III: For measurements performed in the building installation at the distribution level such as on

hardwired equipment in fixed installation and circuit breakers.

Cat. IV: For measurements performed at the primary electrical supply (<1000V) such as on primary

overcurrent protection devices, ripple control units, or meters.

RECEIVING YOUR SHIPMENT

Upon receiving your shipment, make sure that the contents are consistent with the packing list. Notify
your distributor of any missing items. If the equipment appears to be damaged, file a claim immediately
with the carrier and notify your distributor at once, giving a detailed description of any damage.

®

Ø=2.52" (64 mm)

Cable max.

1.97 x 5.31" (50 x 135 mm) or

2.52 x 3.94" (64 x 100 mm)
Bus Bar max.

12.40"

(315 mm)

P1 P2

4.72"

(120 mm)

ELECTRICAL SPECIFICATIONS

Current Range:

1 to 500A AC continuous cycle
1 to 1000A AC continuous cycle
1 to 1500A AC continuous cycle

Transformation Ratio:

500:1, 1000:1, 1500:1

Output Signal:

2 mA AC/A AC (1A at 500A)
1 mA AC/A AC (1A at 1000A)

0.66 mA AC/A AC (1A at 1500A)

1.89"

(48 mm)

Red Black

S2S1

Accuracy and Phase Shift*:
500A RANGE

Primary current 25A 100A 500A

Accuracy % 4% 3% 3%

Phase shift 4° 3.5° 2°

Load Impedance: 5Ω
Overload: 700A for 10 mn
Ampere Second Product: 6 A.s
Accuracy: Per IEC 185-26-27

5 VA Class 3 from 48 to 1000 Hz