This section provides overview, applications, and principles of high voltage probes. Also, please take a look at the list of 8 high voltage probe manufacturers and their company rankings.
High voltage probe is passive probes that can measure high voltages.
In high-voltage measurements that exceed several hundred volts, standard voltage probes break down and cannot be used. Probes have difficulty adapting to high frequencies and voltages.
High voltage probe, on the other hand, can measure voltages as high as several thousand to several tens of thousands of volts and are passive probes dedicated to high voltages. However, when measuring high voltages at high frequencies, the probes quickly heat up, so care must be taken to avoid burns or accidents.
When selecting a probe, the frequency bandwidth, input resistance, input capacitance, operating voltage range, and compatible oscilloscope model must be considered.
Among them, high voltage probes for high-voltage measurement are used to measure waveforms of voltages higher than 1,000 volts and are sometimes used for signal measurement of motor drivers, switching power supplies, inverters, and converters that use power devices such as IGBTs.
They are also often used in cases where high voltage loads such as DC circuits are considered and are also utilized for measuring the anode voltage of cathode ray tubes.
A probe is a physical and electrical connection between a test point, or signal source, and an oscilloscope. There are two main types of connections, some with a single cable and others such as active differential probes.
When measuring high voltages, high voltage probes with attenuation ratios such as 100:1 or 1,000:1 are used.
High-voltage circuits generally have very high internal impedance, so the input impedance of the probe should be considered when employing it.
It is also necessary to check the rating of the voltage probe since the maximum allowable voltage of a voltage probe has the property of decreasing with increasing frequency.
Specifically, the probe is installed between the input terminal and the oscilloscope input section, and the waveform passing through it is measured.
When measuring high-frequency signals, the input capacitance becomes a load and affects the signal, but by connecting the probe through a probe with the attenuation ratio as described above, more accurate waveforms can be measured.
Among high voltage probes, the structure differs depending on the voltage range to be measured. Products of about 25KV DC sold by oscilloscope manufacturers can be handled in the same way as general probes.
On the other hand, there are some products from manufacturers specializing in high voltage probes that can measure voltages of 100KV DC or higher, but such probes are designed to be fixed to a floor or other surface.
High voltage probes consist of three components: the probe itself, a matching box, and a cable connecting them. Since the system under testing is high voltage, long cables (3m to 10m) are available so that measurements can be taken from remote positions.
Safety measures are also a feature of high voltage probes. Probes designed for hand-held operation have a large guard ring to prevent discharge to the human body.
The main body of the probe, which is designed to be fixed, has a terminal for grounding the probe itself.
The inside of the probe is filled with insulating oil or gas to enhance withstand voltage performance.
The matching box performs phase compensation, and the adjustment procedure is more complicated than that for ordinary passive probes because of the large attenuation of the attenuator and the use of long cables. In some cases, the manufacturer of the high voltage probes may ship the probe after adjustment and prohibit the user from making adjustments.
The input resistance of the probe itself depends on the attenuator's attenuation but is usually large, ranging from 100 MΩ to 1,500 MΩ.
An isolated probe is one in which only the probe is floating. It is electrically isolated from the oscilloscope body.
There are two ways to isolate the probe. One is to use a transformer to separate the probe tip from the oscilloscope, and the other is to convert the electrical signals received at the probe tip to photoelectric signals, transmit them through an optical fiber, and return them to the original signals at the receiver side. In both cases, there is no electrical continuity between the probe and oscilloscope, and they are insulated from each other, but the signal detected by the probe is transmitted to the oscilloscope side.
Because of this configuration, even though the oscilloscope itself is properly grounded, it has no effect on the signal of the circuit under test that is applied between the tip of the isolated probe and the ground lead. Thus, even if the circuit under test has very high common-mode voltages, the isolation probe can be used to measure only the differential voltage between the tip and ground lead.
Several isolation probes are available to meet different needs, including multi-channel isolation probes with ground leads isolated from each other. If the isolated probe is to be placed away from the oscilloscope body to prevent electric shock, the fiber-optic type is advantageous.
As with differential probes, frequency bandwidth and common-mode rejection ratio (CMRR) are important characteristics of isolated probes, and isolated probes have superior performance in these areas.
On the other hand, the maximum operating voltage reaches the realm of high voltage probes, with typical models capable of 600 V RMS or 850 V (DC + peak AC).
*Including some distributors, etc.
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