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CT3681 & CT3683
User Manual
OUTPUT ≤ ±7 V INTO 1 MΩ
OFFSET
ADJUST
POWER
1000x
100x
ATTENUATION
RATIO
OVER
RANGE
CT3681
70 MHz
Dierential Probe
5000 Vrms MAX
CAT I
+
Common
Mode
D
ierential
Mode
DC + AC peak
± 7000 V
± 7000 V
@ 1000x
± 700 V
@ 100x
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Safety Summary
To avoid personal injury and/or product damage, review and comply
with the following safety precautions. These precautions apply to both
operating and maintenance personnel and must be followed during all
phases of operation, service, and repair of this probe.
A
WARNING statement calls attention to an operating procedure,
practice, or condition, which, if not followed correctly, could result in
injury or death to personnel.
A
CAUTION statement calls attention to an operating procedure,
practice, or condition, which, if not followed correctly, could result in
damage to or destruction of parts or the entire product. This probe is
intended for usage within Measurement Category I (CAT I) only.
Do Not Work Alone
Do not work alone when working with high voltages.
Inspect the Probe
Inspect the probe and accessories for cracks and frayed or broken
leads before each use. If defects or damages are noted, DO NOT USE
the probe.
Dry Conditions
Hands, shoes, oor and work bench must be dry. Avoid making
measurements under humidity, dampness or other environmental
conditions that might affect safety.
Do Not Remove the Probe’s Casing
Removal of the probe’s casing may expose you to electric shock.
If necessary, disconnect the inputs and outputs of the probe before
opening the case.
Hazardous Contact
To avoid injury, remove jewelry such as rings, watches, and other
metallic objects. Do not touch exposed connections and components
when power is present.
Unexpected Charges
Hazardous voltages may be present in unexpected locations in circuitry
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being tested when a fault condition in the circuit exists. Capacitors
inside the instrument may retain a charge even if the instrument is
disconnected from its source of supply.
Use Only in Ofce-Type Indoor Setting
The probe is designed to be used in ofce-type indoor environments.
Do not operate the probe:
z In the presence of noxious, corrosive, or flammable fumes,
gases, vapors, chemicals, or finely-divided particulates.
z In environments where there is a danger of any liquid being
spilled on the probe.
z In air temperatures exceeding the specified operating
temperatures.
z In atmospheric pressures outside the specified altitude limits
or where the surrounding gas is not air.
Not for Critical Applications
This probe is not authorized for use in contact with the human body or
for use as a component in a life-support device or system.
Do Not Substitute Parts
Do not install substitute parts or perform any unauthorized modication
to the instrument.
Only Qualied Personnel
Only qualied personnel should use this probe. This differential
voltage probe is designed to be used by personnel who are trained,
experienced, or otherwise qualied to recognize hazardous situations
and who are trained in the safety precautions necessary to avoid
possible injury when using such a device.
Observe Maximum Working Voltage
Do not use the CT3681 or CT3683 probe above 5000 Vrms CAT I
(1000x attenuation) or 500 Vrms CAT I (100x attenuation) between the
two input leads. Do not use the probes above 5000 Vrms CAT I (both
100x and 1000x attenuation settings) between each input lead and
earth.
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Use Proper Power Source
To ensure this probe function well, use four AA cells or 6VDC/200mA or
regulated 9VDC/120mA mains adapter or power leads. Do not operate
this probe from a power source that applies more than the voltage
speci ed.
Must be Grounded
This probe is grounded by the shell of the BNC connector through the
grounding conductor of the power cord of the measurement instrument.
Before making connections to the input leads of this probe, ensure
that the output BNC connector is attached to the BNC connector of
the measurement instrument, and that the measurement instrument
is properly grounded. Whenever it is likely that the ground protection
is impaired, you must make the instrument inoperative and secure it
against any unintended operation.
Use Fused Test Prods if Necessary
If this probe is intended to use for measurements in circuits of
installation CAT II, it should incorporate the use of fused test probes.
Compliance Statements
Disposal of Old Electrical & Electronic Equipment
(Applicable in the European Union and other European
countries with separate collection systems). This product
is subject to Directive 2012/19/EU of the European
Parliament and the Council of the European Union on
waste electrical and electronic equipment (WEEE), and in
jurisdictions adopting that Directive, is marked as being
put on the market after August 13, 2005, and should not
be disposed of as unsorted municipal waste. Please utilize
your local WEEE collection facilities in the disposition of
this product and otherwise observe all applicable requirements.
This probe is in compliance with IEC-61010-031 CAT I, Pollution
Degree 2.
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1 Introduction
1.1 Overview
Differential probes allow safe, accurate measurement between two
voltage points where neither point is referenced to ground. The
CT3681 and CT3683 both offer a 70 MHz bandwidth and can test up
to ±7 kV (DC + AC peak). Compatible with oscilloscopes from all major
manufacturers, the probes can be battery operated, powered by a
universal adapter (optional), or powered by USB power lead (optional)
if the oscilloscope is so equipped.
Features:
z Meets IEC 61010-031 safety standard
z 70 MHz bandwidth (-3 dB)
z Up to ±7 kV differential and common mode voltage
z Selectable attenuation settings of 100x/1000x
z Compatible with most oscilloscopes
z Power and over-range indicators
z High accuracy (±2%)
z High CMRR
z Unique high voltage input leads and hook probes (CT3683)
z Powered by 4 AA batteries (included)
z Power adapter, CT3723 (optional)
z USB power lead, CT4122 (optional)
1.2 Initial Inspection
This probe is tested prior to shipment. It is therefore ready for
immediate use upon receipt. An initial physical inspection should be
made to ensure that no damage has been sustained during shipment.
After the inspection, verify the contents of the shipment. The kit
contains:
z Differential probe (with high voltage input leads, CT3683)
z (2) Hook probes, black & red (1000 V for CT3681) (7000 V for
CT3683)
z (4) AA batteries
z Offset adjustment tool
z User manual
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2 Product Description
2.1 Front Panel CT3681
Output BNC
cable, 90 cm,
with 4 mm
Banana Plug
Ground Lead
Hook Probes
Attenuation
Function Switch
Power On/O Switch
LED Power Indicator
Leads,
60 cm
Over-range Indicator
O set Adjustment
Figure 1 Front Panel Diagram CT3681
OUTPUT ≤ ±7 V INTO 1 MΩ
OFFSET
ADJUST
POWER
1000x
100x
ATTENUATION
RATIO
OVER
RANGE
CT3681
70 MHz
Dierential Probe
5000 Vrms MAX
CAT I
+
Common
Mode
D
ierential
Mode
DC + AC peak
± 7000 V
± 7000 V
@ 1000x
± 700 V
@ 100x
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2.2 Front Panel CT3683
OUTPUT ≤ ±7 V INTO 1 MΩ
OFFSET
ADJUST
POWER
1000x
100x
ATTENUATION
RATIO
OVER
RANGE
CT3681
70 MHz
Dierential Probe
5000 Vrms MAX
CAT I
+
Common
Mode
D
ierential
Mode
DC + AC peak
± 7000 V
± 7000 V
@ 1000x
± 700 V
@ 100x
CT3683
Output BNC
cable, 90 cm,
with 4 mm
Banana Plug
Ground Lead
High
Voltage
Hook
Probes
High Voltage
Input Leads
Attenuation
Function Switch
Power On/O Switch
LED Power Indicator
Over-range
Indicator
Oset
Adjustment
Figure 2 Front Panel Diagram CT3683
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3 Using the Probe
3.1 Replacing the Batteries
Before using the differential probe for the rst time, the batteries
supplied with the device must be inserted in the battery compartment
(unless you are using the power adapter or USB power lead).
WARNING
At the time of inserting or replacing the batteries, the input leads must
not be connected to an item to be tested. Never operate the probe with
the case open.
Slide back the battery cover. If necessary, the old AA batteries can then
be removed and the new ones inserted into the compartment. Always
ensure the batteries are positioned for proper polarity. After inserting
the batteries, close the case. When the batteries are low, the power
indicator will start to icker and dim.
3.2 Inspection Procedure
1. Connect the BNC output connector to the vertical input of a
general purposed oscilloscope.
2. Power on the probe.
3. Set the oscilloscope input to DC coupling and 1V/div. Center
the trace on the display.
4. Set the range of the probe to 1/100.
5. Connect the hook probes to the leads.
6. Connect the black hook probe to the ground connection on
the oscilloscope and the red hook probe to the test signal on
the oscilloscope (1 kHz for example).
7. A wave matching the test signal should display on the
screen of the oscilloscope and this means this probe is
working properly.
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3.3 Getting Started
1. Connect the hook probes to the leads.
2. Connect the probe to the oscilloscope with the BNC cable.
When using a portable or ungrounded oscilloscope, connect
the output ground lead to ground.
3. Switch the probe “ON.”
4. Switch to the desired attenuation ratio. When measuring
signals below 700 V, switch the attenuation ratio to
100x in order to get higher resolution and less noise
ratio. Otherwise, set the attenuation ratio to 1000x when
measuring signals up to 7000 V.
5. Use the hook probes to contact the circuit to be tested.
CAUTION
This probe is used to carry out differential measurements between
two points on the circuit under test. This probe is not for electrically
insulating the circuit under test and the measuring instrument.
3.4 Overrange Indicator
The overrange indicator lights when the voltage of the input signal
exceeds the linear operating range of the probe. When this happens,
the signal on the probe output may not accurately represent the signal
on the probe input.
3.5 Vertical Scale on Oscilloscope
The actual vertical scale of the oscilloscope is equal to the attenuation
factor multiplied by the range of vertical scale selected on the
oscilloscope. For example, with the CT3681 set on attenuation 100x,
the oscilloscope on 0.5 V/div, the real vertical scale is 100 x 0.5 = 50 V/
div. With the probe on 1000x, the real vertical scale is 100 x 0.5 = 500
V/div. These values apply when the oscilloscope is set to the typical 1
MΩ impedance input. When the oscilloscope is set to 50 Ω input, the
actual vertical scale will be doubled: 100 V/div for the 100x setting and
500 V/div for the 1000x setting. See Table 1.
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Vertical Scale on Oscilloscope
Scope Input
Impedance
Probe
Attenuation
Setting
Actual
Attenuation
Setting
Vertical Scale
Reading on the
Oscilloscope
Actual Vertical
Scale of the
Oscilloscope
1 MΩ 100x 100x 0.5 V/div 50 V/div
1 MΩ 1000x 1000x 0.5 V/div 500 V/div
50 Ω 100x 200x 0.5 V/div 100 V/div
50 Ω 1000x 2000x 0.5 V/div 1000 V/div
Table 1 Oscilloscope Readings
Offset Zero Procedure
The CT3681 and CT3683 can be adjusted to zero the probe’s offset
voltage using the offset adjustment tool supplied with the probe. Follow
this procedure to perform the offset adjustment.
1. Connect the probe to Channel 1 of the oscilloscope. Turn
on the probe power. You may use the USB power cable or
batteries to power the probe. Set the probe attenuation ratio
to 100x.
2. Short the + and - probe inputs together with the hook tips.
3. Turn on power to the oscilloscope. Leave both the
instrument and the probe turned on for 30 minutes to
stabilize.
4. Press [Default Setup] and [Auto] on the oscilloscope.
5. Press the Channel 1 button, then press the Probe softkey
and set the attenuation to 100x.
6. Set the oscilloscpe to DC coupled mode and the scope
offset to 0 volts.
7. Set the oscilloscope to average mode (x16) or high-
resolution mode to reduce oscilloscope noise.
8. Using the offset adjustment tool (included), adjust the probe
offset voltage to 0 volts
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4 Cleaning
This probe does not require any particular cleaning. If necessary, clean
the case with a cloth slightly moistened with soapy water. Make sure
the probe is completely dry before reconnecting it to an oscilloscope.
WARNING
Dry the probe thoroughly before attempting to make voltage
measurements.
CAUTION
Do not subject the probe to solvents or solvent fumes as these can
cause deterioration of the probe body and cables.
Specications
All specications apply to the unit after a temperature stabilization time of 20 minutes over an
ambient temperature range of 25 °C ± 5 °C.
Electrical Specications
CT3681 & CT3683
Bandwidth (-3dB) 70 MHz (driving 1 MΩ oscilloscope input)
Rise Time (10%-90%) 5 ns
Attenuation ratio 100x/1000x
Accuracy ±2%
CMRR (typical)
-80 dB @ 50 Hz
-60 dB @ 20 kHz
Maximum Differential
Input Voltage
(DC + AC peak)
±700 V @ 100x attenuation
±7000 V @ 1000x attenuation
Maximum Common
Mode Input Voltage
(DC + AC peak)
±700 V @ 100x attenuation
±7000 V @ 1000x attenuation
Absolute Maximum
Rated Input Voltage
(each side to ground)
5000 Vrms CAT I
Input Impedance
50 MΩ // 7 pF (each side to ground)
100 MΩ // 5 pF (between inputs)
Output Voltage Swing ±7 V (driving 1 MΩ oscilloscope input)
Offset (typical) ±5 mV (adjustable)
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Electrical Specications
Noise (typical) 0.9 mVrms
Source Impedance 50 Ω
Power Supply
4 AA batteries (included) or
CT3723 power adapter (optional)
CT4122 USB power lead (optional)
Mechanical Characteristics
Weight 500 g (probe only)
Dimensions 202 x 83 x 38 mm
BNC Cable Length 90 cm
Input Leads Length 60 cm each
CT3681 Probes 1000 V, CAT III, 20 A
CT3683 Probes 7000 V, CAT I, 2 A
Environmental Characteristics
Operating Temp/Humidity -10°C to 40°C / 25% to 85% RH
Storage Temp/Humidity -30°C to 70°C / 25% to 85% RH
Pollution Degree Pollution Degree 2
Altitude
Operating: 3,000 m
Nonoperating: 15,300 m
Safety Specications
IEC 61010-031 CAT I
Specications are subject to change without notice. To ensure the most current version of this
manual, please download the current version from our website: caltestelectronics.com.
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5 Voltage Derating Curve
The derating curve of the absolute maximum input voltage in common
mode is show as follows:
CT3681 & CT3683 Maximum Input Voltage Derating Curve
5000 5000
2500
200
20
10
7
10
8
Figure 3 Derating Curve
10
5
10
100
1,000
10,000
10
6
Frequency (Hz)
Voltage (Vrms)
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6 Service & Warranty Information
6.1 Limited One-Year Warranty
Cal Test Electronics warrants this product to be free from defective
material or workmanship for a period of 1 year from the date of original
purchase. Under this warranty, Cal Test Electronics is limited to
repairing the defective device when returned to the factory, shipping
charges prepaid, within the warranty period.
Units returned to Cal Test Electronics that have been subject to abuse,
misuse, damage or accident, or have been connected, installed or
adjusted contrary to the instructions furnished by Cal Test Electronics,
or that have been repaired by unauthorized persons, will not be
covered by this warranty.
Cal Test Electronics reserves the right to discontinue models, change
specications, price, or design of this device at any time without notice
and without incurring any obligation whatsoever.
The purchaser agrees to assume all liabilities for any damages and/or
bodily injury which may result from the use or misuse of this device by
the purchaser, his employees, or agents.
This warranty is in lieu of all other representations or warranties
expressed or implied and no agent or representative of Cal Test
Electronics is authorized to assume any other obligation in connection
with the sale and purchase of this device.
6.2 Service
If you have a need for calibration or repair services, technical or sales
support, please contact us:
22820 Savi Ranch Parkway
Yorba Linda, CA 92887
800-572-1028 or 714-221-9330
caltestelectronics.com
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© 2016 Cal Test Electronics20161213
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