Patent Description:
In the prior art, test and measurement devices such as oscilloscopes are known that comprise several analog input channels which are also called measurement channels. Typically, oscilloscopes have four analog input channels that can be used to perform measurements on a single device under test or several devices under test, in particular simultaneously.

However, certain test scenarios require more than four analog input channels in order to measure the desired characteristics and properties of a certain device under test. For instance, the switch-on behavior of a device under test, in particular the power sequencing, of several voltages on a certain device under test may be verified simultaneously. For those measurements, the user has to use oscilloscopes that have more than four analog input channels. However, these oscilloscopes are expensive and the high number of analog input channels is used rarely.

<CIT> shows an oscilloscope with a digitizer input and several analog inputs allocated to an analog to digital converter, wherein a digital measurement probe having an analog to digital converter can be connected to the digitizer input.

<CIT> shows a conventional measurement probe having a tip and a ground line wherein respective outputs are provided for being connected with two analog inputs of an oscilloscope. <CIT> shows an oscilloscope with removable extension modules. The oscilloscope has a digitizer for processing the analog signals provided by the extension modules.

Further relevant documents are <CIT>, <CIT>, <CIT>, <CIT> and <CIT>.

Accordingly, there is a need for a cost-efficient possibility to perform measurements that require several analog input channels.

The invention provides an electrical test and measurement device with four analog channels, wherein each analog channel comprises an analog input, an attenuator circuit, an amplifier unit, and a digitizer such that each analog channel has its own digitizer, wherein the electrical test and measurement device comprises another digitizer allocated to a digitizer input of the electrical test and measurement device, wherein the digitizer input is configured to be connected to a measurement extension device so that the number of analog channels of the electrical test and measurement device is increased by the measurement extension device to be connected to the electrical test and measurement device, and wherein the digitizer input is configured to process signals each having several analog signals inputted to the separately formed measurement extension device.

The invention further provides a measurement extension device for being connected to an electrical test and measurement device, wherein the measurement extension device has at least two analog channels each comprising an analog input, an attenuator circuit, and an amplifier unit, wherein the measurement extension device has a common analog output interface with which the analog channels are each connected so that the measurement extension device is configured to increase the number of analog channels of the electrical test and measurement device. Each analog channel further comprises an isolating unit configured to isolate the analog output interface from at least one of the attenuator circuit and the amplifier unit.

Furthermore, the invention provides a test and measurement system comprising a test and measurement device as described above and a measurement extension device for being connected to an electrical test and measurement device, wherein the measurement extension device has at least two analog channels each comprising an analog input, an attenuator circuit, and an amplifier unit, wherein the measurement extension device has a common analog output interface with which the analog channels are each connected so that the measurement extension device is configured to increase the number of analog channels of the electrical test and measurement device.

The invention is based on the finding that the electrical test and measurement device can be extended by using a separately formed measurement extension device that is connected to the digitizer input. The digitizer input is configured to process signals each having several analog signals inputted to the separately formed measurement extension device. Thus, the number of analog channels can be increased by using the separately formed measurement extension device that is connected to the electrical test and measurement device. The measurement extension device is connected to the electrical test and measurement device, in particular its digitizer input, via the analog output interface. Thus, the analog output interface is configured to forward signals that each has several analog signals being inputted to the measurement extension device previously. In general, the analog output interface ensures transmission of high bandwidth signals in a cost-efficient manner compared to a digitized signal. The analog signals forwarded to the test and measurement device are digitized internally.

Thus, several analog channels are provided additionally when the measurement extension device is connected to the test and measurement device. The several analog channels are combined within the measurement extension device and afterwards outputted via a single line that is provided between the analog output interface of the measurement extension device and the digitizer input of the electrical test and measurement device. Accordingly, complex measurements or measurements on complex devices under test can be performed such as measuring power rail sequencing devices that require more than four channels simultaneously.

The analog channels provided at the test and measurement device may be labeled as internal analog channels whereas the analog channels provided due to the connection to the measurement extension device may be labeled as external analog channels.

The electrical test and measurement device already provides the possibility to perform measurements while using integrated analog channels that are also called internal analog channels. Thus, the measurement extension device to be connected to the electrical test and measurement device is used to increase the number of analog channels appropriately for certain measurement requiring more analog channels than provided by the test and measurement device itself.

According to another aspect, a signal processing unit is provided. The signal processing unit of the electrical test and measurement device is used to process the signals received via the analog channels as well as the digitizer input. Accordingly, the processing unit of the electrical test and measurement device is configured to process the signals forwarded via the digitizer input wherein these signals may comprise different analog signals being inputted to the measurement extension device.

Particularly, the signal processing unit has a predetermined maximum sample rate processing power. The sample rate may be <NUM> Giga Samples/second (GS/s).

Further, the signal processing unit may comprise at least one decimator configured to decimate the sample rate. Thus, it is ensured that the maximum sample rate processing power is split appropriately such that the several signals forwarded via the internal analog channels and the external analog channels relating to the digitizer input are processed in a homogeneous manner. Accordingly, the decimator distributes the maximum sample rate processing power homogeneously. For instance, the maximum sample rate processing power of <NUM> GS/s are divided into 8x <NUM> GS/s for four internal analog channels and four external analog channels established by the external measurement extension device connected to the electrical test and measurement device.

According to a certain embodiment, the electrical test and measurement device is an oscilloscope. Typically, an oscilloscope is used to process analog signals.

With regard to the measurement extension device according to the invention, each analog channel further comprises an isolating unit configured to isolate the analog output interface from at least one of the attenuator circuit and the amplifier unit. This isolating unit may provide a galvanic isolation such that offset voltages can be lowered that occur due to the connection of the separately formed measurement extension device. The isolating unit may comprise at least one of an isolating transformer, an optical element, and a capacitive isolator.

Particularly, the isolating unit comprises a power supply interface. Thus, the measurement extension device, in particular its amplifier unit, is powered by the electrical test and measurement device when the measurement extension device is connected to the electrical test and measurement device.

Further, the isolating unit may comprise an isolated control signal interface configured to control the amplifier unit. Thus, the amplifying is also controlled by the electrical test and measurement device.

Generally, the isolation unit ensures that the different signals do not interfere with each other.

According to a certain embodiment, a time delay compensation unit is provided that is configured to compensate time delays introduced by the analog channel, in particular wherein the time delay compensation unit comprises a switch unit allocated to the analog input wherein the switch unit is configured to switch between a calibration signal interface and an input channel allocated to the analog input. This ensures that the occurrence of time delays can be compensated appropriately wherein the time delay occurring is previously determined by comparing a calibration signal sent to the amplifier unit via the calibration signal interface and the calibration signal received by the amplifier unit. This time delay can be calculated and compensated afterwards.

The analog output interface may be configured to be connected with a test and measurement device. The measurement extension device is connected via its analog output interface to the digitizer input of the electrical test and measurement device such that the digitizer input of the electrical test and measurement device corresponds to the number of analog inputs of the measurement extension device.

Moreover, the amplifier unit may comprise a variable gain amplifier. The variable gain amplifier is used for high dynamic input and high input bandwidth. Accordingly, the measurement extension device can be used for signals being dynamic and broadband.

The measurement extension device has in particular four analog channels.

The invention will now be described with reference to the enclosed drawings. In the drawings:.

In <FIG>, a test and measurement system <NUM> is shown that comprises an electrical test and measurement device <NUM> that is established by an oscilloscope <NUM> as well as a measurement extension device <NUM> that is connected to the test and measurement device <NUM>.

In the shown embodiment, the test and measurement device <NUM> has four analog channels <NUM> that each comprises an analog input <NUM>, for instance a BNC input. The analog inputs <NUM> are positioned such that they can be connected easily, for instance at an outer surface of the test and measurement device <NUM>.

Further, the test and measurement device <NUM> comprises a digitizer input <NUM> that is connected to the separately formed measurement extension device <NUM>. The connection is established by a cable <NUM>, for instance a flat conductor. In general, the cable <NUM> used ensures transmission of high bandwidth signals.

Moreover, the test and measurement device <NUM> has a display <NUM> that is configured to illustrate signals received via the analog channels <NUM>. Further, the display <NUM> is configured to display signals received via the digitizer input <NUM>.

As shown in <FIG>, the measurement extension device <NUM> has four analog channels <NUM> that each comprises an analog input <NUM>.

Further, the measurement extension device <NUM> has an analog output interface <NUM> that is connected to the cable <NUM> such that the connection between the test and measurement device <NUM> and the measurement extension device <NUM> is established via the cable <NUM> that connects the digitizer input <NUM> and the analog output interface <NUM>. Due to the analog output interface <NUM>, analog signals are transmitted via the cable <NUM> towards the test and measurement device <NUM>.

As shown in <FIG>, the test and measurement device <NUM> may comprise a housing <NUM> wherein the measurement extension device <NUM> comprises an outer box <NUM> for encompassing the internal components shown in <FIG> as will be described later.

In <FIG>, the test and measurement device <NUM> is shown in more detail as internal components are illustrated, in particular a functional unit <NUM>.

In the shown embodiment, each analog channel <NUM> of the electrical test and measurement device <NUM> comprises an attenuator circuit <NUM>, an amplifier unit <NUM> and a digitizer <NUM> besides the analog input <NUM>. As shown, the amplifier unit <NUM> comprises a variable gain amplifier <NUM> that is used for signals having a high dynamic and high input bandwidth.

The analog channels <NUM> are each allocated to a signal processing unit <NUM> that comprises different processing portions <NUM>. In the shown embodiment, two different processing portions <NUM> are provided wherein each processing portion <NUM> is allocated to two different analog channels <NUM>.

The signal processing unit <NUM> is further connected to a memory <NUM>, in particular a random access memory, that may also comprise different memory portions <NUM> as shown in <FIG>.

Despite the analog channels <NUM> having there own digitizers <NUM>, another digitizer <NUM> is provided that is allocated to the digitizer input <NUM> configured to receive analog signals. Thus, the signals received via the digitizer input <NUM> are digitized by the digitizer <NUM> that is also connected to the signal processing unit <NUM>, in particular a signal processing unit portion <NUM>.

In the input channel allocated to the digitizer input <NUM>, the analog signals received are directly forwarded to the digitizer <NUM>. Thus, no amplifying and/or attenuation of the signals input via the digitizer input <NUM> take place within the test and measurement device <NUM>.

The signal processing unit <NUM>, in particular the signal processing unit portion <NUM> connected to the digitizer input <NUM>, comprises a decimator <NUM> that is used to adapt the sample rate such that the predetermined maximum separate processing power of the signal processing unit <NUM> is not exceeded.

For instance, the predetermined maximum sample rate processing power is <NUM> GS/s wherein the decimator <NUM> decimates the sample rate of the several analog channels <NUM> as well as the digitizer input <NUM> such that 8x <NUM> GS/s are provided for the four internal analog channels <NUM> as well as the four external analog channels <NUM> established by the measurement extension device <NUM>.

Hence, the overall maximum sample rate processing power being available is split in a homogenous manner for all active analog channels <NUM>, <NUM>.

In an alternative embodiment, the decimator <NUM> is allocated to a certain processing portion <NUM> without affecting the other processing portion(s) <NUM> such that only the maximum sample rate processing power of the processing portion <NUM> is decimated appropriately.

In <FIG>, the measurement extension device <NUM> is shown in more detail, in particular its internal components.

Each analog channel <NUM> of the measurement extension device <NUM> comprises an attenuator circuit <NUM> that is connected to the corresponding analog input <NUM> and an amplifier unit <NUM> that comprises a variable gain amplifier <NUM>.

The amplifier unit <NUM> is connected with an isolating unit <NUM> that is shown in <FIG> in more detail.

Generally, the different analog channels <NUM> are each connected with the common analog output interface <NUM> as shown in <FIG>.

In <FIG>, a single analog channel <NUM> is shown in more detail wherein the isolation unit <NUM> is also illustrated in more detail.

The isolation unit <NUM> comprises an isolated control signal interface <NUM> that is configured to control the amplifier unit <NUM>. The isolator control signal interface <NUM> may be provided by an optical isolation such that a galvanic isolation is established.

Further, the isolation unit <NUM> comprises a power supply interface <NUM> that is also isolated with respect to the other signal lines as shown in <FIG>. The power supply interface <NUM> is used to power the amplifier unit <NUM> appropriately.

Accordingly, the measurement extension device <NUM> is controlled by the test and measurement device <NUM>, in particular via the isolated control signal interface <NUM> wherein the amplifier unit <NUM> of the measurement extension device <NUM> is also powered by the test and measurement device <NUM> when the measurement extension device <NUM> is connected to the digitizer input <NUM>.

In <FIG>, another detail of a single analog channel <NUM> is shown. Each analog channel may comprise a time delay compensation unit <NUM> that is configured to compensate time delays introduced by the analog channel <NUM>, in particular its components such as the amplifier unit <NUM>.

As shown in <FIG>, the time delay compensation unit <NUM> comprises a switch unit <NUM> that is connected to a calibration signal interface <NUM> as well as an input channel <NUM> that is provided between the analog input <NUM> and the amplifier unit <NUM>. Particularly, the time delay compensation unit <NUM> may be established as a part of the amplifier unit <NUM>.

Hence, it is ensured that the time delay compensation unit <NUM> is allocated to the analog input <NUM> which is fed by a signal to be processed appropriately.

As shown in <FIG>, the time delay compensation unit <NUM> may generate a calibration signal wherein a calibration signal sent to the amplifier unit <NUM>, in particular the variable gain amplifier <NUM>, is compared with a signal received from the amplifier unit <NUM> in order to determine the occurring time delay T. Thus, the time delay T of the amplifier unit <NUM>, in particular the variable gain amplifier <NUM>, can be determined appropriately and thus compensated.

The several analog inputs <NUM> of the measurement extension device <NUM> may be established by BNC inputs.

Claim 1:
An electrical test and measurement device (<NUM>) with four analog channels (<NUM>), wherein each analog channel (<NUM>) comprises an analog input (<NUM>), an attenuator circuit (<NUM>), an amplifier unit (<NUM>), and a digitizer (<NUM>) such that each analog channel (<NUM>) has its own digitizer (<NUM>), wherein the electrical test and measurement device (<NUM>) comprises another digitizer (<NUM>) allocated to a digitizer input (<NUM>) of the electrical test and measurement device (<NUM>), wherein the digitizer input (<NUM>) is configured to be connected to a measurement extension device (<NUM>) so that the number of analog channels of the electrical test and measurement device (<NUM>) is increased by the measurement extension device (<NUM>) to be connected to the electrical test and measurement device (<NUM>), and wherein the digitizer input (<NUM>) is configured to process signals each having several analog signals inputted to the separately formed measurement extension device (<NUM>).