Greenlee CM-750 User manual

999 3789.1 © 2002 Greenlee Textron IM 1464 REV 1 3/02
CM-700 • CM-750
DIGITAL CLAMP-ON
METERS
MEDIDORES DIGITALES
CON PINZA
MULTIMETRES
NUMERIQUES A
PINCES
INSTRUCTION MANUAL
INSTRUCTION MANUAL
MANUAL DE INSTRUCCIONES
MANUEL D’INSTRUCTIONS
Read and understand all of the instructions and safety
information in this manual before operating or servicing this tool.
Lea y entienda todas las instrucciones y la información sobre
seguridad que aparecen en este manual, antes de manejar estas
herramientas o darles mantenimiento.
Lire attentivement et bien comprendre toutes les instructions et
les informations sur la sécurité de ce manuel avant d‘utiliser ou de
procéder à l‘entretien de cet outil.

2
Description
The Greenlee CM-700 and CM-750 Digital Clamp-on Meters are hand-held testing devices with
the following measurement capabilities: AC and DC voltage, AC and DC current, and
resistance. They also verify continuity. The display holds a measurement for later viewing or
holds the maximum reading. The CM-750 is a true RMS reading meter.
The jaw can accommodate a conductor up to 35 mm (1.38") in diameter. In addition, the
meters feature the following:
•Autoranging
•Zeroing key for DC amps
•Selectable auto power off
•Circuit protection to 600 volts
•100 mA resolution up to 400 amps
Safety
Safety is essential in the use and maintenance of Greenlee tools and equipment. This
instruction manual and any markings on the tool provide information for avoiding hazards and
unsafe practices related to the use of this tool. Observe all of the safety information provided.
Purpose
This instruction manual is intended to familiarize all personnel with the safe operation and
maintenance procedures for Greenlee CM-700 and CM-750 Digital Clamp-on Meters.
Keep this manual available to all personnel.
Replacement manuals are available upon request at no charge.
Greenlee and are registered trademarks of Greenlee Textron.
KEEP THIS MANUAL

CM-700 • CM-750
3
Important Safety Information
Read and understand this material before operating or servicing
this equipment. Failure to understand how to safely operate this
tool can result in an accident causing serious injury or death.
This symbol is used to call your attention to hazards or unsafe practices which could
result in an injury or property damage. The signal word, defined below, indicates the
severity of the hazard. The message after the signal word provides information for
preventing or avoiding the hazard.
SAFETY ALERT SYMBOL
Immediate hazards which, if not avoided, WILL result in severe injury or death.
Hazards which, if not avoided, COULD result in severe injury or death.
Hazards or unsafe practices which, if not avoided, MAY result in injury or property
damage.

4
Important Safety Information
Electric shock and fire hazard:
•Do not expose this unit to rain or moisture.
•Do not use the unit if it is wet or damaged.
•Use test leads or accessories that are appropriate for the application. See the
category and voltage rating of the test lead or accessory.
•Inspect the test leads or accessory before use. They must be clean and dry, and the
insulation must be in good condition.
•Use this unit for the manufacturer’s intended purpose only, as described in this
manual. Any other use can impair the protection provided by the unit.
Failure to observe these warnings can result in severe injury or death.
Electric shock hazard:
•Do not apply more than the rated voltage between any two input terminals, or
between any input terminal and earth ground.
•Do not contact the test lead tips or any uninsulated portion of the accessory.
Failure to observe these warnings can result in severe injury or death.
Electric shock hazard:
Contact with live circuits can result in severe injury or death.

CM-700 • CM-750
5
Important Safety Information
•Do not operate with the case open.
•Before opening the case, remove the test leads (or jaw) from the circuit and shut off
the unit.
Failure to observe these warnings can result in severe injury or death.
•Do not attempt to repair this unit. It contains no user-serviceable parts.
•Do not expose the unit to extremes in temperature or high humidity.
See Specifications.
Failure to observe these precautions can result in injury and can damage the unit.
Do not change the measurement function while the test leads are connected to a
component or circuit.
Failure to observe this precaution can result in injury and can damage the unit.
•Unless measuring voltage or current, shut off and lock out power. Make sure that
all capacitors are discharged. Voltage must not be present.
•Using this unit near equipment that generates electromagnetic interference can
result in unstable or inaccurate readings.

6
Identification
1. Jaw
2. Lever
3. Common (COM) input terminal
4. Volts or resistance (V-Ω) input terminal
5. Display
6. Selector
7. Zero amp DC button and beeper on/off
8. Hold/maximum button
Display Icons
9. Low battery
10. –Polarity indicator
11. Direct current
12. Alternating current
13. Autoranging
14. Hold is enabled
15. Maximum value is displayed
16. Root mean square (CM-750 only)
17. Continuity indicator
18. M Mega (106)
19. k Kilo (103)
20. ΩOhms
21. m Milli (10-3)
22. V Volts
23. A Amps
24. 30.00 Numeric display
Symbols on the Unit
Warning —Read the instruction manual
Double insulation
1
28
7
6
5
3 4
12
11
10
921–23
18–20
17
13 14 15 16
24

CM-700 •CM-750
7
Using the Features
•HOLD/MAX
Press momentarily to hold the present value on the display. Press again to return to normal
mode.
To use the Maximum Hold function, press and hold before turning the unit on. Press again
to reset the stored maximum value. Press and hold for 2 seconds to return to normal
display. To remove the Maximum Hold function, turn the unit off and then back on.
•ZERO A /Ω/
For DC current measurements, close the jaw around the conductor. Orient the jaw for a
positive reading for greatest accuracy. Remove the jaw from the conductor and close it.
Press the ZERO A button. This compensates for residual magnetism in the jaw. Place the
jaw over the conductor, keeping the same orientation, and take the reading.
For continuity measurements, press to enable tone. The icon appears on the display,
and the meter switches to the 400 Ωrange. Press again to measure resistance.
•Auto Power Off Disable
Turn the selector to the OFF position. Press and hold the ZERO A /Ω/button while
quickly turning the selector to the Ω/position. The unit will now stay on until the
selector is set to OFF or until the battery is depleted (approximately 150 hours for a fresh
alkaline battery).
The next time the unit is turned on, the 30-minute Auto Power Off will be enabled.

8
Waveform
RMS Value 100 100 100 100
Average Value 90 100 87 64
Crest Factor* 1.414 1 1.73 2
(ξ)
AC Measurement
AC measurements are usually displayed as RMS (root mean square) values. The RMS value is
equal to the value of a DC waveform, which would deliver the same power if it replaced the
time-varying waveform. Two AC measurement methods are average-responding RMS
calibrated and true RMS-reading.
The average-responding RMS calibrated method takes the average value of the input signal
after full wave rectification, multiplies it by 1.11, and displays the result. This method is
accurate if the input signal is a pure sine wave. The Greenlee CM-700 is an average-
responding meter.
The true RMS-reading method uses internal circuitry to read the true RMS value. This method
is accurate, within the specified crest factor limitations, whether the input signal is a pure sine
wave, square wave, triangle wave, half wave, or signal with harmonics. The ability to read true
RMS provides much more measurement versatility. The Greenlee CM-750 is a true RMS meter.
The Waveforms and Crest Factors table shows some typical AC signals and their RMS values.
Waveforms and Crest Factors
*The crest factor is the ratio of the peak value to the RMS value; it is represented by the
Greek letter ξ.

CM-700 • CM-750
9
1. Set the selector according to the Settings Table.
2. See Typical Measurements for specific measurement instructions.
3. Test the unit on a known functioning circuit or component.
• If the unit does not function as expected on a known functioning circuit, replace the
battery.
• If the unit still does not function as expected, send the unit to Greenlee for repair. See
the address shown under Warranty.
4. Take the reading from the circuit or component to be tested.
5. If it is a DC reading, remove the clamp from the circuit and press the ZERO A /Ω/
button. Clamp the jaw around the circuit again to measure the actual DC current.
Settings Table
*Tone sounds if the measured resistance is less than approximately 50 Ω, and turns off
when greater than approximately 300 Ω.
Electric shock hazard:
Contact with live circuits can result in severe injury or death.
Operation
To measure set the selector connect the and connect the
this value … to this symbol … red lead to … black lead to …
Ω/
Continuity* and press V-ΩCOM
ZERO A /Ω/
Resistance Ω/V-ΩCOM
DC Voltage VV-ΩCOM
AC Voltage VV-ΩCOM
DC Current (600 A max.) ARemove lead Remove lead
AC Current (600 A max.) ARemove lead Remove lead

10
Typical Measurements
Current Measurement—
Clamp Around Wire
Notes:
•Clamp the jaw around one conductor
only.
•Close the jaw completely to ensure
accurate measurement.
•Center the wire in the jaw for highest
accuracy.
Voltage
Measurement
Note: For DC measurements, current
flowing through the jaw in the direction
indicated by the arrow produces a
positive reading. Position the jaw for a
positive reading for highest accuracy.