Extech CT70 Operating Manual

User's Guide

AC Circuit Load Tester

Model CT70

Introduction

Congratulations on your purchase of the CT70 AC Circuit Load Tester.

This device can detect circuit and wiring problems such as: Poor ground impedance, false
grounds, missing ground fault protection, low voltage availability under load, and high
ground-to-neutral voltage. In addition, the CT70 tests GFCI and EPD circuits.

Circuit and wiring issues listed above can introduce shock hazards (from grounding issues)
and can comprise performance of machinery and equipment (from poor ground impedance,
lack of sufficient voltage under load and/or high ground-to-neutral voltage). In addition, fire
can result from the heat generated by high resistance points in a circuit.

Proper wiring habits have been shown to greatly increase power quality performance.

This meter is shipped fully tested and calibrated and, with proper use, will provide years of
reliable service.

Features

• True RMS measurements

• Voltage drop measurements on 12A, 15A, and 20A loads

• Voltage measurements: Line, ground-to-neutral, and peak

• Measures frequency of the voltage

• Checks 3-wire receptacle configuration

• Finds false grounds

• Tests GFCI and EPD circuits

Safety

International Safety Symbols

This symbol, adjacent to another symbol or terminal, indicates the user
must refer to the manual for further information.

This symbol, adjacent to a terminal, indicates that, under normal use,
hazardous voltages may be present

Double insulation

WARNING

CAUTION

This WARNING symbol indicates a potentially hazardous situation,
which if not avoided, could result in death or serious injury.

This CAUTION symbol indicates a potentially hazardous situation, which
if not avoided, may result damage to the product.

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Description

Meter Description

1. AC power cable connection

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2. Measurement results menu

3. Hot-Neutral-Ground coded measurement result

4. Primary reading display

5. Secondary reading display

6. Down arrow button

7. Right arrow button

8. GFCI test button

Display Description

A Amperes (Current)
V Voltage
Vd Voltage Drop
% Percent Voltage Drop
VL Voltage load
Z Impedance
Hz Hertz (cycles per second)

Ω Ohms (Resistance)
mS Milliseconds
ASCC Available Short Circuit Current
Peak Ground to positive peak measurement
RMS Root Mean Square
GFCI Ground Fault
EPD Equipment Protection Device test
NEUT Neutral
OL Overload
m, M, k Unit of measure prefixes: milli, mega, and kilo

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CT70 V7.0 09/10

Operation Overview

The CT70 AC Circuit Load Tester can test outlets or circuits under load for proper wiring,
reverse polarity, and the presence of a ground. The CT70 uses a simple menu-driven
display to allow the user to quickly see line voltage, voltage drop under full load, ground-to­neutral voltage, and line impedance. The GFCI testing utility is performed separately per
UL-1436, disrupting the flow of electricity if a functioning GFCI is present.

Note: To avoid the buildup of heat during load testing, allow at least 20 seconds to elapse
between tests. In addition to the safety benefits, this will allow the meter to maintain its
stated accuracy during repeated tests.

Warning: To avoid damage to the instrument, do not use this device on the output
of a UPS system, a light dimmer, or a square wave generator.

Warning: Use only the supplied power/test cord (CT70-AC) with this equipment

Interpreting Measurement Results

Important note: The CT70 is a microprocessor controlled device that prioritizes its tasks.
Taking a reading and analyzing the results are its top priorities. This is why, at times, the
keypad may not respond immediately. The internal computer places a higher priority on
completing a test than on recognizing a keystroke. To minimize this effect, press and hold a
key until the display menu changes.

In addition to the main Wiring Configuration icon, shown on the meter display, the
measurement modes are accessed using the four (4) menu items shown on the left side of
the display. The menu items are:

1. Voltage (V)

2. Voltage drop (Vd)

3. ASCC (Available short circuit current)

4. Impedance (Z)

Use the ▼ button to scroll the menu list.

The wiring configuration screen shows correct wiring, reverse polarity wiring, and ‘no
ground’ conditions. The three circles on the wiring configuration icon indicate the wiring
status. The circles are coded, changing appearance (clear, solid, and flashing) to indicate
the measurement results. A table is provided below for interpreting the circle code.

Blue Display

Red Display

Red Display

Blank Display

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