USER GUIDE True RMS 300A AC Mini Clamp Meter with Non‐ Contact Voltage Detector Model MA140
Introduction Thank you for selecting the Extech MA140 300A AC True RMS Mini Clamp Meter with Non‐Contact Voltage Detector. The MA140 is small in size but rugged in performance. The MA140 measures AC current to 300A and offers a Smart Data Hold feature, display Backlight, In‐rush Current mode, Low Pass Filtering (LPF), and a non‐contact Volt‐Detection feature that senses electrical sources safely. This device is shipped fully tested and calibrated and, with proper use, will provide years of reliable service.
CAUTIONS CAUTIONS identify conditions and actions that could cause DAMAGE to the meter or equipment under test. Do not expose the meter to extremes in temperature or high humidity. Safety Symbols that are typically marked on meters and instructions This symbol, adjacent to another symbol, indicates the user must refer to the manual for further information.
Description Meter Description 1. Transformer current jaw 2. Finger‐Hand Guard 1 3. Jaw opening trigger 4. LCD Multi‐function display 5. Push‐button controls 2 5 3 Note that the battery compartment is located on back of meter 4 Display Description 1. Non‐Contact Volt Detect icon 2. Main Display digits 3. In‐Rush Current mode 4. Low Pass Filter 5. Data Hold 6. AC Measurement 7. Amperes (current) 8. Battery status icon 9.
Operation CAUTIONS Read and understand all of the Safety statements listed in the safety section of this manual prior to use. Powering the Meter 1. Press the Power‐Backlight button to power the meter. Check the batteries if the unit fails to power ON. 2. Press and hold the Power button for more than 2 seconds to power OFF the meter. 3. The meter has an Auto Power OFF feature (APO) where the meter switches OFF after 20 minutes of inactivity. To disable APO, refer to the next section.
AC Current Measurements WARNING: Do not handle the meter above the finger/hand guard barrier. CAUTION: Observe CAT III 600V with respect to Earth Ground for the Jaw. 1. Press the ‘A’ button to access the AC Current measurement mode. The A symbol will appear on the display in the lower right hand side indicating Amperes (Amps). 2. Press the jaw trigger to open the clamp jaw. 3. Position the clamp around only one conductor. See accompanying diagrams for correct and incorrect use. 4.
Inrush Current Mode In the Inrush mode the meter waits until at least 5A is detected and then starts a 100ms sample window in which to capture an inrush current RMS value. Refer to illustration below. 1. Press and hold the INRUSH button for > 2 seconds to access the Inrush Current mode. 2. The display will show the INRUSH icon. 3. When ready, take a current measurement. The meter will capture the highest reading detected during a 100ms window.
Volt‐Detection Feature The meter’s audible beeper triggers and the display shows dashes when the meter senses an electrical voltage field. The higher the electrical field strength the greater the number of dashes displayed and the faster the rate of the audible beeps. If the meter does not emit a tone or display dashes in this mode, there is still the possibility that voltage is present. Please use caution. 1. Press the ‘V’ button to access the Non‐Contact Voltage Detect mode. 2.
Maintenance WARNING: To avoid electrical shock, disconnect the meter from any circuit and turn OFF the meter before opening the case. Do not operate with an open case. Cleaning and Storage Periodically wipe the case with a damp cloth and mild detergent; do not use abrasives or solvents. If the meter is not to be used for 60 days or more, remove the batteries and store them separately. Battery Replacement 1. Remove the Phillips head screw at the lower back of the meter. 2. Open the battery compartment.
Specifications ELECTRICAL SPECIFICATIONS Function Range Resolution 60.00 A 0.01 300.0 A 0.1 Accuracy (of reading) 50/60Hz ± (2.0% + 5 digits) AC Current All specifications are valid from 10% to 100% of each range The LCD displays 0 counts when the reading < 10 counts 60.00 A 0.01 ± (3.5% + 5 digits) 300.0 A 0.
GENERAL SPECIFCATIONS Display Over‐range indication Conversion rate Maximum conductor size 6000‐count Multi‐Function LCD “OL” or “‐OL” is displayed 2 updates per second 22mm (0.87”) in diameter Low battery indication is displayed.
