Rohde & Schwarz RT-ZD40 User manual

R&S®RT-ZD40
Active Differential Probe
User Manual
User Manual
Version 05
1410536302
(>:ÃÍ2)

This User Manual describes the following R&S®RT-ZD models and options:
●R&S®RT-ZD40 (1410.5205.02)
© 2019 Rohde & Schwarz GmbH & Co. KG
Mühldorfstr. 15, 81671 München, Germany
Phone: [phone] - 0
Fax: [phone]
Email: [email protected]
Internet: www.rohde-schwarz.com
Subject to change – Data without tolerance limits is not binding.
R&S® is a registered trademark of Rohde & Schwarz GmbH & Co. KG.
Trade names are trademarks of the owners.
1410.5363.02 | Version 05 | R&S®RT-ZD40
Throughout this manual, products from Rohde & Schwarz are indicated without the ® symbol and without
product type numbers, e.g. R&S®RT-ZD40 is indicated as R&S RT-ZD40.

Contents
R&S®RT-ZD40
3User Manual 1410.5363.02 ─ 05
Contents
1 Product Description.............................................................. 5
1.1 Key Features and Key Characteristics............................................... 5
1.1.1 Key Characteristics................................................................................. 5
1.1.2 Key Features...........................................................................................6
1.2 Unpacking..............................................................................................7
1.2.1 Inspecting the Contents.......................................................................... 7
1.3 Description of the Probe...................................................................... 8
1.3.1 Probe Head.............................................................................................8
1.3.2 Probe Box............................................................................................... 9
1.4 Accessories and Items....................................................................... 10
1.4.1 Accessories Supplied............................................................................11
1.4.2 Optional Accessories............................................................................ 12
1.4.3 Service Accessories..............................................................................13
2 Putting into Operation.........................................................14
2.1 Connecting the Probe to the Oscilloscope...................................... 15
2.2 Identification of the Probe..................................................................16
2.3 Using the Probe.................................................................................. 16
2.3.1 Zero Adjustment....................................................................................16
2.3.2 Micro Button..........................................................................................17
2.4 Offset Compensation..........................................................................17
2.4.1 Differential Offset.................................................................................. 17
2.4.2 Common Mode Offset...........................................................................18
2.4.3 R&S ProbeMeter...................................................................................20
3 Connecting the Probe to the DUT...................................... 22

Contents
R&S®RT-ZD40
4User Manual 1410.5363.02 ─ 05
4 Characteristics of Differential Probes............................... 27
4.1 Common Mode Rejection Ratio (CMRR)...........................................28
4.2 Dynamic Range and Operating Voltage Window............................. 29
4.3 Ground Connection............................................................................ 30
5 Measurement Principles..................................................... 31
5.1 Signal Integrity of the Transferred Signal.........................................33
5.1.1 Bandwidth............................................................................................. 33
5.1.2 Connection Inductance......................................................................... 34
5.1.3 CMRR................................................................................................... 37
5.2 Signal Loading of the Input Signal....................................................37
5.2.1 Signal Loading for Differential Input Signals......................................... 38
5.2.2 Signal Loading for Non-Differential Input Signals................................. 40
5.3 Probing Philosophy............................................................................ 40
6 Maintenance and Service....................................................42
6.1 Cleaning...............................................................................................42
6.2 Contacting Customer Support...........................................................42
6.3 Returning for Servicing...................................................................... 43
6.4 Calibration Interval............................................................................. 44
6.5 Discarding the Product...................................................................... 44
6.6 Spare Parts.......................................................................................... 44
7 Functional Check.................................................................47
Index..................................................................................... 48

Product Description
R&S®RT-ZD40
5User Manual 1410.5363.02 ─ 05
1 Product Description
1.1 Key Features and Key Characteristics
The R&S RT-ZD40 is a differential probe with high input impedance. It is used for
differential voltage measurements from DC to 4.5 GHz.
Differential probes can be used for single-ended and differential applications.
They are equipped with two high-impedance inputs and can measure the voltage
between any two test points. Unlike using single-ended probes, there is no need
to ensure that one of the test points is always at ground potential.
The comprehensive accessory set allows this probe to be connected to a wide
variety of devices under test (DUT). Provided with special features such as the
R&S ProbeMeter and the micro button, the R&S RT-ZD40 is designed to meet
tomorrow's challenges in probing.
The probe is equipped with theRohde & Schwarz probe interface. It can be con-
nected to any Rohde & Schwarz instrument that is compatible with this interface.
When connected to the front panel, the probe is controlled by the oscilloscope's
software. Supported oscilloscopes are listed in the data sheet.
Using a specially developed adapter (see Chapter 1.4.2, "Optional Accessories",
on page 12), the probe can also be connected to any other base unit.
1.1.1 Key Characteristics
The key characteristics of the probe are the following:
Key Features and Key Characteristics

Product Description
R&S®RT-ZD40
6User Manual 1410.5363.02 ─ 05
Bandwidth DC to 4.5 GHz
Dynamic range
(differential input)
±5 V with ±5 V offset capability
10 V AC (Vpp)
Operating voltage window
(each pin to GND)
±8 V with ±22 V common mode offset capability
Available for R&S RT-ZD40 probes with serial number
≥ 200000
Maximum non-destructive input voltage ±30 V
Between each signal pin and ground
Diff. input resistance 1 MΩ
Diff. input capacitance 0.4 pF
R&S ProbeMeter, measurement error <0.1 %
Extremely low zero and gain errors throughout the entire temperature range, no significant tem-
perature drift
Micro button
Rohde & Schwarz probe interface
1.1.2 Key Features
Micro button
The micro button at the probe head can remotely control different functions on the
base unit. The assigned function is configured via the base unit.
For details, see Chapter 2.3.2, "Micro Button", on page 17.
R&S ProbeMeter
The R&S ProbeMeter measures the DC voltage of the input signal directly at the
probe tip. It provides a continuous high-precision DC voltage measurement that is
independent of the settings of the oscilloscope and runs in parallel to the time
domain measurement. If activated on the base unit, the measured value is dis-
played on the screen of the Rohde & Schwarz oscilloscope.
The R&S ProbeMeter simultaneously measures both differential and common
mode DC voltages.
For details, see Chapter 2.4.3, "R&S ProbeMeter", on page 20.
Key Features and Key Characteristics

Product Description
R&S®RT-ZD40
7User Manual 1410.5363.02 ─ 05
Data memory
The probe has an integrated data memory, containing the individual probe correc-
tion parameters (e.g. gain, delay, offset). These parameters are read out and pro-
cessed by the Rohde & Schwarz oscilloscope. As a result, the probe offers a high
degree of accuracy, and additional calibration procedures are not required.
1.2 Unpacking
The carrying case contains the following items:
●R&S RT-ZD40 differential probe
●Carrying case
●Accessory boxes
●User manual
●R&S RT-ZD40 data sheet
●Calibration certificate
●Documentation of calibration values (if
ordered)
1.2.1 Inspecting the Contents
●Inspect the package for damage.
Keep the package and the cushioning material until the contents have been
checked for completeness and the device has been tested.
If the packaging material shows any signs of stress, notify the carrier and your
Rohde & Schwarz service center. Keep the package and cushioning material
for inspection.
●Inspect the probe.
If there is any damage or defect, or if the R&S RT-ZD40 differential probe
does not operate properly, notify your Rohde & Schwarz service center.
●Inspect the accessories.
If the contents are incomplete or damaged, notify your Rohde & Schwarz ser-
vice center.
Unpacking

Product Description
R&S®RT-ZD40
8User Manual 1410.5363.02 ─ 05
Accessories supplied with the device are listed in Chapter 1.4.1, "Accessories
Supplied", on page 11.
1.3 Description of the Probe
The probe consists of the probe head for connection to the DUT, the probe box
for connection to the oscilloscope, and the probe cable.
1.3.1 Probe Head
The small and lightweight probe head is designed for easy handling and high-per-
formance measurements. The probe head is used for connecting the probe and
the DUT. Different accessories for the signal and ground sockets allow the probe
head to be connected to a wide range of DUTs.
(1) Positive signal socket
(2) Negative signal socket
(3) Ground socket
(4) Micro button
The accessories supplied for the probe head
sockets are listed in Chapter 1.4.1, "Accesso-
ries Supplied", on page 11.
The ground socket is compatible with 0.64 mm
(25 mil) square pins and 0.6 mm to 0.8 mm
(24 mil to 35 mil) round pins.
Spacing of signal sockets: 4 mm (160 mil).
Description of the Probe

Product Description
R&S®RT-ZD40
9User Manual 1410.5363.02 ─ 05
Special accessories for signal sockets
The signal sockets of R&S RT-ZD40 have a special design to ensure opti-
mal performance. The signal sockets are not compatible to standard acces-
sories based on 0.64 mm (25 mil) square pins or 0.8 mm (35 mil) round
pins. Use only special accessories for R&S RT-ZD40 provided by
Rohde & Schwarz.
1.3.2 Probe Box
The probe box connects the probe and the oscilloscope via the Rohde & Schwarz
probe interface. The Rohde & Schwarz probe interface contains a male precision
7 mm (276 mil) BNC connector and six pogo pin connectors. This interface pro-
vides the required supply voltage and is also used to transmit analog signals and
digital data simultaneously. All the analog voltages required by the probe are gen-
erated in the probe box. This approach ensures that it will be possible to operate
future probes on any base unit that features a Rohde & Schwarz probe interface.
(1) Rohde & Schwarz probe interface with
7 mm (276 mil) coaxial connector and 6 pogo
pins
(2) Release knob
Connect the R&S RT-ZD40 only to an instrument with Rohde & Schwarz probe
interface. Never connect it to a usual BNC jack. Although the 7 mm coaxial con-
nector looks like a standard BNC connector, it is constructed differently and does
not fit to the standard BNC jack. The interface of the R&S RT-ZD40 can withstand
a higher frequency limit.
Description of the Probe

Product Description
R&S®RT-ZD40
10User Manual 1410.5363.02 ─ 05
1.4 Accessories and Items
The figure below shows all accessories that are available for the R&S RT-ZD40
differential probe.
Figure 1-1: Available accessories
The R&S RT-ZA15 external attenuator is not a accessory of the R&S RT-ZD40.
Putting the R&S RT-ZA15 on the R&S RT-ZD40 can damage both parts mechani-
cally.
Accessories and Items

Product Description
R&S®RT-ZD40
11User Manual 1410.5363.02 ─ 05
1.4.1 Accessories Supplied
The following table shows the accessories supplied with the R&S RT-ZD40 differ-
ential probe.
Table 1-1: Accessories supplied
Item Quantity Description
100 Signal pin, solder-in
2Socket adapter, variable
spacing
2 Browser adapter, rigid
2Browser adapter, spring-
loaded
2 Lead, 6 cm / 2.4 in
1 Lead, 15 cm / 5.9 in
2 Mini clip
Accessories and Items

Product Description
R&S®RT-ZD40
12User Manual 1410.5363.02 ─ 05
Item Quantity Description
2 Micro clip
1 Marker band kit
1Carrying case with foam
inlay
For a list of spare parts, see Chapter 6.6, "Spare Parts", on page 44.
1.4.2 Optional Accessories
If the delivered accessories do not meet individual customer requirements,
Rohde & Schwarz offers different accessory sets for sale. The order numbers are
provided in the data sheet.
Table 1-2: R&S RT ‑ ZA4 mini clips
Item Quantity Description
Mini clip 10 Contains mini clips.
Table 1-3: R&S RT ‑ ZA5 micro clips
Item Quantity Description
Micro clip 4 Contains micro clips.
Accessories and Items

Product Description
R&S®RT-ZD40
13User Manual 1410.5363.02 ─ 05
Table 1-4: R&S RT ‑ ZA6 lead set
Item Quantity Description
Lead, 6 cm / 2.4 in
Lead, 15 cm / 5.9 in
5
5
Contains short and long leads.
Table 1-5: R&S RT ‑ ZA8 differential pin set
Item Quantity Description
Signal pin, solder-in
Socket adapter, variable spacing
Browser adapter, rigid
Browser adapter, spring-loaded
100
2
2
2
Contains the pins available for
the R&S RT-ZD40.
Table 1-6: R&S RT ‑ ZA9 probe box to N / USB adapter
The adapter can be used to connect the R&S RT-
ZD40 differential probe to any other oscilloscope or
any other measurement instrument (e.g. a network
or spectrum analyzer).
Using the USB interface of the adapter, the probe
can be powered and controlled from any conven-
tional PC.
1.4.3 Service Accessories
To order accessories for servicing the probe, contact your Rohde & Schwarz ser-
vice center. The following accessories are available:
Table 1-7: Service accessories
Item Description
R&S RT-ZK2 The service kit is used to calibrate the probe, to do perform-
ance tests, and for servicing. The service kit includes all
adapters and accessories to connect the probe to the
required measuring instruments.
R&S RT-ZD40 Service Manual The service manual contains a detailed description of the
performance test to verify the specifications, and other
important service procedures.
Accessories and Items

Putting into Operation
R&S®RT-ZD40
14User Manual 1410.5363.02 ─ 05
2 Putting into Operation
The probe is designed for usage with oscilloscopes that have a Rohde & Schwarz
probe interface. Supported Rohde & Schwarz oscilloscopes are listed in the pro-
be's data sheet.
Read and observe the printed "Basic Safety Instructions" that are delivered with
the probe. Also, read and observe the safety instructions of the oscilloscope the
probe is connected to.
Maximum non-destructive input voltage
The maximum non-destructive input voltage is ±30 V. A higher input voltage
can destroy the probe. The maximum non-destructive input voltage of a dif-
ferential probe is specified as the maximum voltage between each signal
pin and ground. The maximum input voltage is derated for higher frequen-
cies. Refer to the data sheet for further information.
Risk of device damage
The R&S RT-ZD40 can withstand a moderate amount of physical and elec-
trical stress. To avoid damage, treat the probe with care:
●Do not exceed the specified voltage limits.
●Connect the R&S RT-ZD40 only to an instrument with Rohde & Schwarz
probe interface. Never connect it to a usual BNC jack. Although the
7 mm coaxial connector looks like a standard BNC connector, it is con-
structed differently and does not fit to the standard BNC jack. The inter-
face of the R&S RT-ZD40 can withstand a higher frequency limit.
●Handle the probe by the probe head or probe box. Avoid excessive
strain on the probe cable, and kinking.
●Prevent the probe from receiving mechanical shock.
●Do not spill liquids on the probe.
●Store the probe in a shock-resistant case, e.g. in the shipping case.

Putting into Operation
R&S®RT-ZD40
15User Manual 1410.5363.02 ─ 05
During usage, the probe slightly heats up. Warming is normal behavior and not a
sign of malfunction.
Damage caused by electrostatic discharge
Electrostatic discharge (ESD) can damage the electronic components of the
probe and the instrument, and also the device under test (DUT). Electro-
static discharge is most likely to occur when you connect or disconnect a
DUT or test fixture to the probe and to the instrument's test ports. To pre-
vent electrostatic discharge, use a wrist strap and cord and connect your-
self to the ground, or use a conductive floor mat and heel strap combina-
tion. Discharge cables and probe tips before you connect them.
2.1 Connecting the Probe to the Oscilloscope
► Connect the probe box (1) to the Rohde & Schwarz probe interface of the
oscilloscope (2).
The probe snaps in when connected properly to the port.
Figure 2-1: Connecting the probe to the Rohde & Schwarz oscilloscope
Connecting the Probe to the Oscilloscope

Putting into Operation
R&S®RT-ZD40
16User Manual 1410.5363.02 ─ 05
► To disconnect the probe:
a) Press and hold the release button (3).
b) Pull the probe box away from the oscilloscope.
2.2 Identification of the Probe
When the probe is connected to the oscilloscope, the oscilloscope recognizes the
probe and reads out the probe-specific parameters.
The oscilloscope settings for attenuation and offset are automatically adjusted.
After the probe is connected to the oscilloscope and the settings are adjusted, the
waveform is shown for the channel to which the probe is connected.
The complete probe information is shown in the probe settings dialog. For more
information, refer to the user manual of your oscilloscope.
2.3 Using the Probe
2.3.1 Zero Adjustment
The zero error can impair the measurement results, therefore, correct the zero
error if necessary. The zero error of the probe itself is very small. However, differ-
ences in DUT and oscilloscope ground levels can cause larger zero errors visible
on the oscilloscope's screen. If the DUT is not floating but ground-referenced, an
zero adjustment improves the measurement results.
The zero error is corrected at the oscilloscope. Depending on the type of the used
oscilloscope, correction is done automatically using the AutoZero function, or
manually ("Zero Adjust" or similar setting). Refer to the oscilloscope's user man-
ual for available functionality and its usage.
1. Connect the probe to the Rohde & Schwarz oscilloscope.
2. Set the oscilloscope to the smallest vertical scale.
3. Short the signal pins and the ground pin together.
Using the Probe

Putting into Operation
R&S®RT-ZD40
17User Manual 1410.5363.02 ─ 05
4. Adjust the zero position of the waveform using the appropriate function of the
oscilloscope ("AutoZero", "Zero Adjust" or similar).
The waveform is set to 0 V on the horizontal centerline of the oscilloscope.
2.3.2 Micro Button
The micro button provides easy and quick access to important functions of the
Rohde & Schwarz oscilloscope. After a function has been assigned, pressing the
micro button remotely controls this specific function on the base unit. For exam-
ple, "Run continuous" or "Run single" are often assigned to the micro button.
The configuration of the micro button is part of the probe settings of the channel
to which the probe is connected. For more details, see the oscilloscope's user
manual.
2.4 Offset Compensation
The R&S RT-ZD40 features two offset compensation functions: a differential off-
set compensation and a common mode offset compensation. Each function com-
pensates a particular DC component of the input signal, even in front of the active
amplifier in the probe tip. For a definition of differential and common mode input
voltages, see Chapter 4, "Characteristics of Differential Probes", on page 27.
2.4.1 Differential Offset
The differential offset compensation is often referred to as offset compensation.
Offset Compensation

Putting into Operation
R&S®RT-ZD40
18User Manual 1410.5363.02 ─ 05
The differential offset function can compensate a DC voltage applied between the
positive and the negative input socket. This is particularly helpful if a small single-
ended signal with a large DC offset is measured with a differential probe, for
example, with the negative input socket connected to ground. As the R&S RT-
ZD40 measures differential voltages, setting a differential offset compensation is
directly visible on the oscilloscope screen as a voltage offset of the measured
waveform.
Figure 2-2: Differential offset compensation for a single-ended measurement (negative
input connected to ground) using an R&S RT ‑ ZD10/20/30
There are several ways to set the offset compensation:
●Use the vertical knob at the oscilloscope if its function is set to offset.
●Enter the offset value in the channel settings or probe settings on the
Rohde & Schwarz oscilloscope.
●Use the micro button to measure input signals with different DC offsets: assign
"Offset to mean" to the micro button. See also Chapter 2.3.2, "Micro Button",
on page 17.
For more details, see the oscilloscope's user manual.
2.4.2 Common Mode Offset
Common mode offset compensation is available for R&S RT‑ZD probes with
serial number ≥ 200 000. It can compensate a common DC voltage applied to
both input sockets (referenced to the ground socket). This is particularly helpful
Offset Compensation

Putting into Operation
R&S®RT-ZD40
19User Manual 1410.5363.02 ─ 05
for measurements on differential signals with high common mode levels, for
example, current measurements using a shunt resistor.
Figure 2-3: Common mode (CM) offset compensation for a differential measurement
If the input signals fit into the operating voltage window of the R&S RT-ZD40, it is
not necessary to set a common mode offset compensation.
The R&S RT-ZD40 measures only differential input signals. Common mode
signals are suppressed by the probe. Therefore, the common mode offset
compensation is not directly visible on the oscilloscope screen, see also
Chapter 4.2, "Dynamic Range and Operating Voltage Window",
on page 29. An incorrect common mode offset compensation can lead to
unwanted clipping effects. Measuring the common mode input voltage
using the R&S ProbeMeter is a convenient way to detect breaches of the
operating voltage window.
Offset Compensation

Putting into Operation
R&S®RT-ZD40
20User Manual 1410.5363.02 ─ 05
If supported by the Rohde & Schwarz oscilloscope, you can set the "CM offset" in
the probe settings on the instrument. For more details, see the oscilloscope's
user manual.
2.4.3 R&S ProbeMeter
The R&S ProbeMeter is an integrated voltmeter that measures DC voltages with
higher precision compared to the oscilloscope's DC accuracy. The DC measure-
ment is performed continuously and in parallel to the time domain measurement
of the oscilloscope.
High-precision measurements are achieved through immediate digitization of the
measured DC voltage at the probe tip.
The R&S ProbeMeter measures the differential and common mode DC voltages
simultaneously and without reconnecting the probe. For a definition of differential
and common mode input voltages, see Chapter 4, "Characteristics of Differential
Probes", on page 27.
When the R&S ProbeMeter is active, the measured values are displayed on the
oscilloscope. The R&S ProbeMeter state is part of the probe settings of the chan-
nel to which the probe is connected. For details, refer to the user manual of the
Rohde & Schwarz oscilloscope.
Advantages of the R&S ProbeMeter:
●Measures DC voltages of different levels, no need to adjust the measurement
range of the oscilloscope.
●True DC measurement (integration time > 100 ms), not mathematical average
of displayed waveform.
●High measurement accuracy and low temperature sensitivity.
●Simple means of setting the oscilloscope's trigger level and vertical scaling if a
waveform is not visible.
●Independent of oscilloscope settings for offset, position, vertical scale, hori-
zontal scale, and trigger.
●Independent of probe settings for measurement mode and gain.
●Unique way to detect unexpected or inadmissible common mode voltages,
e.g. bias points - measurement of common mode DC voltages without recon-
necting the probe.
●Differential measurement range ±5 V + offset compensation setting.
Offset Compensation