CT70 V7.0 09/10
6
Testing Procedures
Test 1: Wiring Verification
The wiring configuration is the first test result that is displayed. Refer to the table presented
earlier in the user guide for the test result key.
For wiring conditions other than normal, the CT70 is limited in the type of tests it can
perform on a circuit until the circuit’s wiring issues are resolved. For ‘no ground’ conditions,
only the line voltage and voltage drop tests can be made. For reverse polarity conditions,
open neutral, or open hot conditions the meter will not display since power will not be
available.
Notes:
•
The meter cannot sense two hot wires in a circuit
•
The meter cannot display the results of more than one circuit issue at time
•
The meter cannot sense ground reversals
Test 2: Voltage Measurements
Warning:
Do not take measurements on circuits with voltages higher than 300VAC
(maximum voltage rating).
Line voltage measurements should be 120VAC ±10% at 60Hz. For noise-free sine waves,
the peak voltage should be 1.414 times the rms line voltage reading. Ground to neutral
voltage should be less than 2 VAC in which case the display backlight will appear blue in
color, if ground to neutral voltage is greater than 2 VAC the backlighting appears in red.
Higher ground to neutral voltages indicates excessive current leakage between the neutral
and ground conductors. Excessive ground to neutral voltage may result in inconsistent or
intermittent equipment performance.
Voltage Measurement Troubleshooting Suggestions
Problems Likely
Causes
Possible Solutions
Out of tolerance Line Voltage
(Line should be 120V±10%)
Overloaded circuit
Redistribute loads
Connection within circuit or
at the panel has excessive
resistance
Repair high resistance
connection
Utility company problem
Contact the power utility
company
High Ground to Neutral voltage
(Readings > 2VAC indicated a
problem)
Neutral to Ground current
leakage
Identify leakage, check for
multiple bonding points
Peak Voltage out of tolerance
(For 120V Line, Peak should
measure between 153 - 183V)
Supply voltage out of
tolerance
Contact power utility company
High peak loads on circuit
Redistribute electronic devices
Frequency out of tolerance
(50/60Hz)
Supply frequency out of
tolerance
Contact power utility company
