AEMC INSTRUMENTS MD303 AC Current Probe User Manual
AC Current Probe Model MD303
User Manual
DESCRIPTION
The MD303 (Catalog #1201.21) is designed for use in industrial environments. The hook-shaped jaws enable the user to “pry” into or “hook” onto cables (will accept 2 x 500 MCM) or even smaller bus bars.
The Model MD303 is compatible with any AC ammeter, multimeter, or other current measurement instruments with an input impedance lower than 5 . To achieve the stated accuracy, use the MD303 with an ammeter having an accuracy of 0.75% or better.
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 600V in overvoltage, category III (CAT III). Use extreme caution when clamping around bare conductors or bus bars



For measurements on circuits not directly connected to the AC supply wall outlet such as protected secondaries, signal level, and limited energy circuits.
For measurements performed on circuits directly connected to the electrical distribution system. Examples are measurements on household appliances or portable tools.
For measurements performed in the building installation at the distribution level such as on hardwired equipment in fixed installation and circuit breakers.
For measurements performed at the primary electrical supply (<1000V) such as on primary
overcurrent protection devices, ripple control units, or meters.
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.

Primary current |
25A | 100 A | 250 A | 500 A |
Accuracy |
4.5% | 3.5% | 3% |
3% |
Phase shift | 4° | 2° | 2° |
2° |
Influence of Adjacent Parallel Conductor: < 30mA/A at 50Hz
Influence of Conductor in Jaw Opening: ± 1.5%
MECHANICAL SPECIFICATIONS
Operating Temperature: -5° to 122°F (-15° to 50°C)
Storage Temperature: -40° to 185°F (-40° to 85°C)
Influence of Temperature: < 0.1% per 10°K
Altitude:
Operating: 0 to 2000 m
Non-operating: 0 to 12,000 m
Jaw Opening: 1.3″ (33mm)
Maximum Conductor Size: 1.18″ (30mm)
Maximum Bus Bar Size: 2.48 x 0.20″ (63 x 5mm)
Envelope Protection: IP 20 (IEC 529)
Drop Test: 1.5m (IEC 68-2-32)
Mechanical Shock: 100g (IEC 68-2-27)
Vibration: 10/55/10Hz, 0.15mm (IEC 68-2-6)
Polycarbonate Material:
Handles: 10% fiberglass charged polycarbonate UL 94 V0
Dimensions: 2.6 x 7.68 x 1.34″ (66 x 195 x 34mm)
Weight: 14.82 oz (420g)
Colors: Dark gray handles
Output:
Double insulated 5 ft (1.5 m) lead with safety banana plugs
SAFETY SPECIFICATIONS

Electrical:
Double insulation or reinforced insulation between the primary or secondary and the outer case of the handle conforms to IEC 1010-2-032. 600V, CAT III, Pollution Degree 2
Electromagnetic Compatibility:
EN 50081-1 Class B EN 50082-2 Electrostatic discharge IEC 1000-4-2 Radiated field IEC 1000-4-3 Fast transients IEC 1000-4-4 Magnetic field at 50/60 Hz IEC 1000-4-8
ORDERING INFORMATION
Current Probe MD303 ……………….. Cat. #1201.21
Accessories:
Banana plug adapter
(to non-recessed plug) ……………….. Cat. #1017.45
OPERATION
Please make sure that you have already read and fully understand the WARNING section on page 1.
Making Measurements with the AC Current Probe Model MD303
- Connect the black and red terminals to the Ampere AC range of your DMM or current measuring instrument. Select the appropriate current range (2A AC range). Clamp the probe around the conductor to be tested with the arrow pointed toward the load. If the reading is less than 200mA, select the lower range until you obtain the best resolution. Read the value display on the DMM and multiply it by the probe ratio (1000/1). (If reading = 0.459A, the current flowing through the probe is 0.459A x 1000 = 459A AC).
- For best accuracy, avoid if possible, the proximity of other conductors which may create noise.
Tips for Making Precise Measurements
- When using a current probe with a meter, it is important to select the range that provides the best resolution. Failure to do this may result in measurement errors.
- Make sure that probe jaw mating surfaces are free of dust and contamination. Contaminants cause air gaps between the jaws, increasing the phase shift between primary and secondary. It is very critical for power measurement
MAINTENANCE:
Warning
- For maintenance use only original replacement parts.
- To avoid electrical shock, do not attempt to perform any servicing unless you are qualified to do so.
- To avoid electrical shock and/or damage to the instrument, do not get water or other foreign agents into the probe.
Cleaning
To ensure optimum performance, it is important to keep the probe jaw mating surfaces clean at all times. Failure to do so may result in error in readings. To clean the probe jaws, use very fine sand paper (fine 600) to avoid scratching the jaw, then gently clean with a soft oiled cloth.
REPAIR AND CALIBRATION
You must contact our Service Center for a Customer Service Authorization number (CSA#). This will ensure that when your instrument arrives, it will be tracked and processed promptly. Please write the CSA# on the outside of the shipping container
. Chauvin Arnoux®, Inc. d.b.a. AEMC® Instruments 15 Faraday Drive Dover, NH 03820 USA 800-945-2362 (Ext. 360) • 603-749-6434 (Ext. 360) • repair@aemc.com (Or contact your authorized distributor)
NOTE: All customers must obtain a CSA# before returning any instrument.
TECHNICAL AND SALES ASSISTANCE
If you are experiencing any technical problems, or require any assistance with the proper use or
application of this instrument, please contact our technical hotline:
800-343-1391 • 508-698-2115 • techsupport@aemc.com
LIMITED WARRANTY
The current probe is warranted to the owner for a period of one year from the date of original purchase
against defects in manufacture. This limited warranty is given by AEMC® Instruments, not by the
distributor from whom it was purchased. This warranty is void if the unit has been tampered with, abused
or if the defect is related to service not performed by AEMC® Instruments.
Full warranty coverage and product registration is available on our website at: www.aemc.com/warranty.html.
Please print the online Warranty Coverage Information for your records.
Documents / Resources
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AEMC INSTRUMENTS MD303 AC Current Probe [pdf] User Manual MD303 AC Current Probe, MD303, AC Current Probe, Current Probe, Probe |