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Portable single-phase watthour meter tester

Probewell offers the most advanced portable single-phase watthour meter tester, the MT-1/NT4. Using the technology developed for our 3-phase tester, the weight of the MT-1/NT4 is only 5.3 lb, making it the smallest portable watthour single-phase meter tester available today!
The MT-1/NT4 can test all common residential watthour meter forms 1S, 2S, 3S, 4S and 12S.
The three loads HL, PF and LL are set automatically according to the TA of the meter being tested. Any non-standard current can be also programmed by the user for special needs.
With the commercial 12S meter, the MT-1/NT4 can test two phases simultaneously or separately. The meter under test is entirely controlled by the test socket. No setup wiring is needed.
The MT-1/NT4 also has reverse flow testing capability for net metering installations.
SKU: NT4 Category:


Two Built-in 50A Current Synthesizers (Phantom Load)

  • Simulates active and reactive loads.
  • Regulated test currents up to 50A.

Built-in Watthour Standard

  • True watthour standard.
  • Stable accuracy within the specified temperature operating range
  • Comes with a complete calibration report certifying measurement accuracy over its entire 36-point operating range using a reference standard traceable to NIST.

Easy to Use

  • Twist and lock removable tab can be placed without tools at 3, 6 or 9 o’clock.
  • Handheld remote control with its intuitive menus.
  • Deadfront design for safer operation.


Compatible Meters
Form 1S, 2S, 3S*, 4S*, 12S
Class 10, 20, 100, 200, 320**
Test Socket
Input Voltage 100 – 600VAC
Line Frequency 58 – 62Hz
Power Consumption 75VA (maximum)
Circuit Breakers 2 x 1A (press-to-reset mechanism)
Current Synthesizers
Adjustable Current 0.25 to 50A
Phase Angle Unity and 60° Lag
Single-Phase Watthour Standard
Typical Accuracy ±0.02%
Guaranteed Accuracy ±0.05%
Operation -4° to 140°F (-20° to 60°C)
Storage -4° to 140°F (-20° to 60°C)
Humidity 5% to 95% (non condensing)
Physical Dimensions
Test Socket (Diam. x D) 6.9” x 7.7”
Remote Control (HxLxD) 8.3” x 3.9” x 1”
Carrying Bag (HxLxD) 11” x 11” x 8”
Test Socket 5.3 lb
Remote Control 0.6 lb
Overall with Carrying Bag 8.0 lb
Parts and Labor 2-years limited***

*May be incompatible with some 3S and 4S form meters.
**An adapter may be required depending on the meter installation.
***Only applicable to units shipped to Canada or USA. 1 year warranty for other countries.