Textron Greenlee CMT-90 User manual

52058189 © 2010 Greenlee Textron Inc. 12/10
CMT-90
Clamp-on Meter
Medidor
con pinza
Contrôleur
numérique
à 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.
Register this product at www.greenlee.com / Registre este producto
en www.greenlee.com / Enregistrez votre produit en ligne, www.greenlee.com

2
Description
The Greenlee CMT-90 Digital Clamp-on Meter is a hand-held testing device with the
following measurement capabilities: AC and DC voltage, AC current, and resistance.
It also tests diodes and verifies continuity. The CMT-90 is a true RMS-reading meter.
This unit automatically determines measurement function based on input. It has a
smart data hold feature with audible and visual alert if the input changes significantly
while the unit is in HOLD mode. The unit automatically enters HOLD mode when the
jaw is removed from a conductor while measuring AC current. It performs a self-test
and displays approximate remaining battery capacity during the power-up sequence.
The Automatic Power Off feature can be disabled if desired.
The display automatically illuminates for easy viewing in dark areas.
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 of This Manual
This instruction manual is intended to familiarize all personnel with the safe opera-
tion and maintenance procedures for the Greenlee CMT-90 Digital Clamp-on Meter.
Keep this manual available to all personnel.
Replacement manuals are available upon request at no charge
at www.greenlee.com.
KEEP THIS MANUAL
All specifications are nominal and may change as design improvements occur.
Greenlee Textron Inc. shall not be liable for damages resulting from misapplication or misuse of
its products.
® Registered: The color green for electrical test instruments is a registered trademark of
Greenlee Textron Inc.
Do not discard this product or throw away!
For recycling information, go to www.greenlee.com.

3
CMT-90
Important Safety Information
SAFETY ALERT SYMBOL
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.
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.
Read and understand this material before operating or
servicing this equipment. Failure to understand how to safely
operate this tool could result in an accident causing serious
injury or death.

4
Important Safety Information
Electric shock hazard:
Contact with live circuits could result in severe injury or death.
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. Refer to
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 could 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 could result in severe injury or death.

5
CMT-90
Important Safety Information
Electric shock hazard:
•Do not operate with the case or battery cover open.
•Before removing the case or battery cover, remove the test leads (or jaw) from
the circuit and shut off the unit.
Failure to observe these warnings could result in severe injury or death.
Electric shock hazard:
•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.
Failure to observe these warnings could result in severe injury or death.
Electric shock hazard:
•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.
Refer to “Specifications.”
•Do not connect to voltage for longer than 30 seconds.
Failure to observe these precautions may result in injury and can damage the unit.
Electric shock hazard:
Do not use the meter to measure voltages in circuits that could be damaged or
actuated by the meter’s low input impedance (approximately 4 kΩ).
Failure to observe this precaution may result in injury and can damage the unit.

6
Identification
1. Jaw
2. Lever
3. Display
4. Common (COM) input terminal
5. Volts or resistance (V-Ω) input terminal
6. ON/OFF/HOLD button
7. Sensor for automatic backlit display
Display Icons
8. Low battery indicator
9. –Polarity indicator
10. Measured voltage is greater than
30 volts AC or DC
11. AutoSense Automatic selection is active
12. Automatic Power Off is enabled
13. AutoHold Hold function is enabled
14. LoZi Low input impedance is active
15. AC AC measurement is selected
16. Continuity
17. DC DC measurement is selected
18. Diode
19. AAmperes
20. VVoltage
21. %Percent
22. kKilo (103)
23. ΩOhms
24. OL Overload indicator
Symbols on the Unit
Warning—Read the instruction manual
Electric shock hazard
Application around and removal from hazardous live conductors is permitted.
Double insulation
Battery
Recycle product in accordance with manufacturer’s directions
Note: Icons that
appear on the display
but are not identified
are not used on this
model.
1
2
3
4 5
6
7
8
9
10
11-12 13-15
16-17
18-20
21-23
24

7
CMT-90
Using the Features
•ON/OFF/HOLD: Momentarily press the ON/OFF/HOLD button to hold the present
measurement on the display; momentarily press again to return to the normal
display mode. Press and hold to turn the unit on or off.
•Smart Hold: The hold feature is disabled when “OL” is displayed on the LCD. The
LCD will blink and the beeper will sound if the unit is in HOLD mode and the input
increases by 5.0 volts or 5.0 amps. It will also blink and flash if the unit is in HOLD
mode and detects an input type change, such as from AC volts to AC amps.
•Auto Hold (AC amps only): The unit automatically holds a stable AC current
measurement that is 3 amps or more. The unit beeps three times to indicate it has
saved the stable value. This value will be displayed for 5 seconds after the unit
is removed from the conductor. The value can be recalled by pressing the HOLD
button. To enable this feature, press and hold the ON/OFF/HOLD button until the
“AutoHold” icon blinks when turning the unit on, approximately 5 seconds.
•Battery Capacity Display: The unit displays the percentage of remaining battery
capacity when it is powering up. Replace the battery when “0%” is shown.
•Power-on Self-test: The unit automatically tests its internal circuitry after it
displays battery capacity. If a problem is found, the LCD will display “FAIL”. Do not
use the meter if “FAIL” is shown on the LCD.
Note: Do not measure while powering up as this could cause an incorrect self-test
failure.
•Automatic Power Off: To extend battery life, the unit will shut itself off after
approximately 20 minutes of inactivity. To disable this feature, press and hold
the ON/OFF/HOLD button until the “APO” icon blinks when turning the unit on,
approximately 3 seconds.

8
AC Measurement
AC measurements are usually displayed as RMS (root mean squared) values. Two
methods of AC measurement are average-responding RMS calibrated and true
RMS-reading.
The average-responding RMS calibrated method takes the average value of the input
signal, multiplies it by 1.11, and displays the result. This method is accurate if the
input signal is a pure sine wave.
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, a square wave, sawtooth wave, half wave or signal with
harmonics. The ability to read true RMS provides much more measurement versatil-
ity. The Greenlee CMT-90 is a true RMS meter.
The Waveforms and Crest Factors table shows some typical AC signals and their
RMS values.
Waveforms and Crest Factors
Waveform
RMS Value 100 100 100 100
Rectified Value 90 100 87 64
Crest Factor*
(x)1.414 1 1.73 2
* The crest factor is the ratio of the peak value to the RMS value; it is represented
by the Greek letter x.

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CMT-90
Operation
Electric shock hazard:
Contact with live circuits could result in severe injury or death.
1. The meter automatically selects the proper measurement according to the
following table.
Priority Display Conditions
1AC volts or DC volts,
whichever is greater
Input at terminals is
1.3 to 999.9 VAC
2.1 to 999.9 VDC
-0.7 to -999.9 VDC
2Resistance and
continuity
Input at terminals is
0 to ∞ Ω
0 to 0.9 VAC
1.0 to 2.0 VDC
-0.2 to -0.4 VDC
3 Diode test Input at terminals is
0.4 to 0.8 VDC
4 AC amps AC current through jaw is
0.9 to 600.0 A
2. Refer to “Typical Measurements” for specific measurement instructions.
3. Test the unit on a known functioning circuit or component of the type you intend
to measure.
•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. Refer to the instructions under the Warranty.
4. Take the reading from the circuit or component to be tested.

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.
Current Measurement—
Clamp Around Line Splitter
Notes:
•The Greenlee 93-30 Line Splitter is divided. One
section renders amps; the other renders amps
multiplied by 10.
•Close the jaw completely to ensure accurate
measurement.
•Center the line splitter in the jaw for highest
accuracy.