Cal Test Electronics CT3684 User manual

CT3684 & CT3685
User Manual

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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.
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
being tested when a fault condition in the circuit exists. Capacitors

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inside the instrument may retain a charge even if the instrument is
disconnected from its source of supply.
Use Only in Ofce-Type Indoor Setting
The probe is designed to be used in ofce-type indoor environments.
Do not operate the probe:
zIn the presence of noxious, corrosive, or flammable fumes,
gases, vapors, chemicals, or finely-divided particulates.
zIn environments where there is a danger of any liquid being
spilled on the probe.
zIn air temperatures exceeding the specified operating
temperatures.
zIn 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 modication
to the instrument.
Only Qualied Personnel
Only qualied personnel should use this probe. This differential
voltage probe is designed to be used by personnel who are trained,
experienced, or otherwise qualied 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 CT3684 or CT3685 above their maximum working
votages. See “Electrical Specications” on page 9.
Use Proper Power Source
Do not operate this probe from a power source that applies more than
the voltage specied.

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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 Probes if Necessary
If this probe is intended to use for measurements in circuits of
installation CAT III, 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 (CT3684) or
CAT II (CT3685), 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 CT3684
and CT3685 both offer 50 MHz bandwidth and can test up to ±700 V
(DC + AC peak) ±1400 V (DC + AC peak) respectively. Compatible with
oscilloscopes from all major manufacturers, the probes are powered by
the included 9 VDC adapter.
Features:
z50 MHz bandwidth (-3 dB)
zUp to ±700 V (DC + AC peak) common mode (CT3684)
zUp to ±1400 V (DC + AC peak) common mode (CT3685)
zAttenuation settings of 10x (CT3684) and 100x (CT3685)
zHigh accuracy (±1%)
zHigh CMRR
zPower indicator LED
z9 VDC adapter, CT3723 (included)
zUSB power lead, CT4122 (optional)
zBattery pack with 4 AA batteries, CT3729 (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:
zDifferential probe
z(2) Hook probes, black & red
zUser manual
z9 VDC adapter, CT3723

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2 Product Description
2.1 CT3684 & CT3685 Description
Output BNC
cable, 90 cm,
with 4 mm
Banana Plug
Ground Lead
Hook ProbesProbe Body
Power On/O Switch
LED Power Indicator
Leads, 50 cm
Figure 1 Front Panel Diagram CT3684 and CT3685
9 VDC
Adapter
Input

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3 Using the Probe
3.1 Power Connection
Connect the 9 VDC adapter to the input on the probe. See Figure 1.
Plug the adapter to power.
WARNING
At the time of powerig on the probe, the input leads must not be
connected to an item to be tested. Never operate the probe with the
case open.
3.2 Optional Battery Pack
If using the optional battery pack, CT3729, the batteries supplied must
be inserted into the battery pack and the pack attached to the probe.
See Figure 2.
Figure 2 Replacing the Batteries
Open the battery compartment. 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.

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3.3 Inspection Procedure
1. Connect the BNC output connector to the vertical input of
the 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 attenuation setting on the oscilloscope to match the
probe 10x (CT3684) and 100x (CT3685).
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.
3.4 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. Set the attenuation setting on the oscilloscope to match the
probe 10x (CT3684) and 100x (CT3685).
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.

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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, using the CT3684, attenuation of 10x, the
oscilloscope on 0.5 V/div, the real vertical scale is 10 x 0.5 = 5 V/div.
With the CT3685, attenuation of 100x, the real vertical scale is 100
x 0.5 = 50 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: 10 V/div for the 10x
probe (CT3684) and 100 V/div for the 100x probe (CT3685). See Table
1.
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 10x 10x 0.5 V/div 5 V/div
1 MΩ 100x 100x 0.5 V/div 50 V/div
50 Ω 10x 20x 0.5 V/div 10 V/div
50 Ω 100x 200x 0.5 V/div 100 V/div
Table 1 Oscilloscope Readings
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.

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Specications
All specications apply to the unit after a temperature stabilization time of 20 minutes over an
ambient temperature range of 25 °C ± 5 °C.
Electrical Specications
CT3684 CT3685
Bandwidth (-3dB) 50 MHz (driving 1 MΩ oscilloscope input)
Rise Time (10%-90%) 7 ns
Attenuation ratio 10x 100x
Accuracy ±1%
CMRR (typical) -90 dB @ 60 Hz
-55 dB @ 1 MHz
Maximum Differential Input
Voltage
(DC + AC peak)
±70 V ±700 V
Maximum Common Mode Input
Voltage
(DC + AC peak)
±700 V ±1400 V
Absolute Maximum Rated Input
Voltage (each side to ground) 500 Vrms CAT I 1000 Vrms CAT II
Input Impedance 1.6 MΩ // 7 pF (each side to
ground)
4.0 MΩ // 7 pF (each side
to ground)
Output Voltage Swing ±7 V (driving 1 MΩ oscilloscope input)
Offset (typical) ±2 mV ±1 mV
Noise (typical) 0.7 mVrms 0.3 mVrms
Source Impedance 50 kΩ
Power Supply
CT3723 power adapter (included) or
4 AA batteries (optional)
CT4122 USB power lead (optional)
Mechanical Characteristics
Weight 300 g
Dimensions 111 x 22 x 14 mm
BNC Cable Length 125 cm
Input Leads Length 50 cm each

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Environmental Characteristics
Operating Temp/Humidity -10°C to 40°C / Up to 85% RH
Storage Temp/Humidity -30°C to 70°C / Up to 85% RH
Pollution Degree Pollution Degree 2
Altitude Operating: 3,000 m
Nonoperating: 15,300 m
Safety Specications
IEC 61010-031 CAT I (CT3684) CATII (CT3685)
Specications 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.
5 Voltage Derating Curve
The derating curve of the absolute maximum input voltage in common
mode is show as follows:
CT3684 & CT3685 Maximum Input Voltage Derating Curve
107108
Figure 3 Derating Curve
1
10
600
20
100
1000
106
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
specications, 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 ElectronicsPart # 450844-001 20161222