IM CL255 17
AC Voltage V (Input impedance: 1MΩ)
(Crest factor (CF): 3.0 or less, peak voltage: 1200V or less)
Measuring Range (Auto-ranging) Accuracy
0 to 39.99V
15.0 to 399.9V
150 to 750V
±1.5% rdg ±3dgt (50/60Hz)
±2.0% rdg ±4dgt (30~1kHz)
Conversion method : AC coupled, true rms responding, calibrated to the rms
Auto-ranging
Lo : 0 to 39.99V (Shifts to Mid at 40.00V)
Mid : 15.0 to 399.9V (Shifts to Lo at 14.9V and to Hi at 400.0V)
Hi : 150 to 750V (Shifts to Mid at 149V. At 770V or above, "OL" is shown.)
Resistance
Ω
Measuring Range (Auto-ranging) Accuracy
0 to 399.9Ω
150 to 3999Ω±1.5% rdg ±2dgt
Auto-ranging
Lo : 0 to 399.9Ω(Shifts to Hi at 400.0Ω)
Hi : 150 to 3999Ω(Shifts to Lo at 149Ω. At 4000Ωor above, "OL" is shown.)
Continuity Check (Range fixed)
Measuring Range Accuracy
10 to 399.9Ω±1.5% rdg ±2dgt
The buzzer beeps when the resistance is 20Ωor less.
Frequency
Measuring Range Accuracy
10 to 3999Hz ±1.5% rdg ±5dgt
OUTPUT (Output impedance: about 10kΩ)
Measuring Range Output voltage (mVDC) Accuracy
0 to ±399.9A 0 to ±399.9mV
DC ±150 to ±2000A ±15.0 to ±200.0mV ±1.5% rdg ±3mV
0 to 399.9A 0 to 399.9mV
150 to 1700A 15.0 to 170.0mV
±1.5%rdg±3mV (50/60Hz)
±3.0%rdg±3mV (40~1kHz)
AC
1701 to 2000A 170.1 to 200.0mV ±3.5%rdg±3mV (50/60Hz)
18 IM CL255
*Effective Value (rms)
Most alternating currents and voltages are expressed in effective values,
which are also referred to as RMS (Root-Mean-Square) values.
The effective value is the square root of the average of square of alternating
current or voltage values.
Many clamp meters using a conventional rectifying circuit have "RMS" scales
for AC measurement. The scales are, however, actually calibrated in terms of
the effective value of a sine wave though the clamp meter is responding to
the average value. The calibration is done with a conversion factor of 1.111
for sine wave, which is found by dividing the effective value by the average
value. These instruments are therefore in error if the input voltage or current
has some other shape than sine wave.
Waveform
Effective
value
Average
value Conversion
factor Reading errors for
average sensing
instruments
Crest factor
CF
0
A
0
A
0
A
0
A
T
ｆ D=f/T
≒0.707
A
1
2A
1
3A
AD
2A
≒0.637
A
0.5A
ｆ
AT
＝A・D
≒1.111
≒11.1%
3
＝－3.8%
A 1.111－A
××100
A
0.5A 1.111－3
××100
A
A
1
2
3
≒1.155
22
AD
AD 1
D
＝(1.11 D－1）
×100％
0％2
≒1.414
1
3
≒1.732
1
D
＝
A
AD
V rms/V avgV avg
V rms
*CF(Crest Factor) is found by dividing the peak value by the effective value.
Examples:
DC: CF=1
Sine wave: CF=1.414
Square wave with a 1:10 duty ratio: CF=3
General Specifications
●Operating System : Dual integration
●Measurement Function : AC current, DC current, AC voltage, DC voltage,
resistance, continuity check, frequency
●Display : Liquid crystal display with maximum counts of 3999
●Overrange Indication : "OL" is shown on the display
IM CL255 19
●Response Time : Approx. 2 seconds.
●Sample Rate : Approx. 3 times per second.
●Temperature and Humidity for Guaranteed Accuracy : 23°C ±5°C, relative
humidity up to 75% without condensation
●Operating Temperature and Humidity : 0 to 40°C, relative humidity up to
85% without condensation
●Storage Temperature and Humidity : -20 to 60°C, relative humidity up to
85% without condensation
●Effect of conductor position : Within ±1.5%rdg ±3dgt of indicated value at
the center to a 10 mm-dia conductor carrying 100A, at every part inside
the jaws
●Effect of external magnetic field : 4A or less in AC or DC magnetic field of
400 A/m
●Power Source : 6LR61 or 6F22 9V battery
●Battery Life : Approx. 15 hours (continuity)
●Current Consumption : Approx. 15mA max.
●Sleep function : Automatically powered down in Approx. 30 minutes after
the last switch operation (power consumption : Approx. 200µA)
●Withstanding Voltage : 5500V AC, 50/60Hz for 1 minute between electrical
circuit and housing case or metal part of the jaws
●Insulation Resistance : 10MΩor greater at 1000V between electrical circuit
and housing case or metal part of the jaws
●Conductor Size : Approx. 55mm diameter max.
●Dimensions : Approx. 105(W) x 250(H) x 49(D) mm
●Weight : Approx. 540g (with battery)
●Safety Standard: EN 61010-1
EN 61010-2-031
EN 61010-2-032
AC/DC 600V CAT III, AC/DC 1000V CAT II,
Pollution degree 2, indoor use
●EMC Standard: EN 61326
EN 55022
●Accessories : Test leads Model 98011············· 1set
6F22 battery······························ 1
Carrying case Model 93034 ······ 1
Output Plug Model 98012·········· 1
User’s Manual ··························· 1
●Optional Accessories : Clamp adapter Model 99025
Output cable for terminal screw Model 91019
20 IM CL255
6. Calibration and After-sales Service
Should any failure occur while you are using the tester, follow the instructions
given below. If the tester still fails to operate correctly and needs repair, con-
tact the vendor from whom you purchased the instrument or the nearest
Yokogawa M&C sales office.
●Turn off the POWER switch once, then turn it back on again.
●If the tester does not turn on, replace the battery with a new one.
Calibration
It is recommended that the instrument be calibrated once every year.
