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The key point that 99% of people tend to overlook when choosing a sensor

Release date:2020-04-07

In test and measurement equipment used at ordinary times, due to the dc voltage test and measurement equipment, the current input value is restricted, in testing, usually used in sensors, used in the selection of sensors, the top issue facing the normally in this case, we usually only care about sensor size whether meet the test requirements, but beyond that, the choice of sensors and many places need to be aware of, this is the most commonly used current sensor, such as hold down to select the appropriate sensors.


Whether the range of the sensor matches the measured signal is the most important indicator and the most likely place for problems to occur. Usually, when choosing, we will pay attention to the range suitable for the instrument itself. Take the lime CTA1000 sensor with PA5000H and 50A power board card as an example. The minimum range of PA5000H is 1A. The minimum display value of the current test instrument is 1.5% of the range, i.e., the value below 15mA cannot be displayed. The variable ratio of the sensor is 1:1000. Therefore, it is better to use PA5000H with 5A board CARDS at this time, because the minimum range of 5A board CARDS is 10mA, and can display the sensor output current value of 0.15ma or more.


If you have purchased a machine, you can use an alternative solution with a patv-33 adapter that converts the current signal of the sensor into a voltage signal for input to the BNC port of the power analyzer.


A, bandwidth


For instruments, sensors, and the bandwidth of the same parameters, especially high frequency signals, such as motor, usually 1 or efficiency is too low, many of which are caused by the sensor bandwidth, according to the barrel effect, the entire bandwidth can be determined by the lowest part of the test system, such as 5 m bandwidth PA5000H 100 k bandwidth sensor, so the system bandwidth is 100 k, only in testing high frequency and low frequency signals measuring difference, may be due to insufficient bandwidth test.


Type of inductor


Current sensor, for example, often have a voltage type current sensor and current current sensor, the principle of them is different, the type of the output signal is different also, most of the hall sensor is usually not a portable sensor, for example, high test precision and can output the lime, CT, LF series, brave CTA series current signal. For this type of sensor, the appropriate proportions can be set immediately in the instrument. Voltage type current sensor is generally BNC port, such as current clamp, oscilloscope current probe, etc., is to convert the current signal into voltage signal, it is necessary to set the corresponding external sensor and variable ratio in the instrument. In addition, for special sensors with integrators (such as roche coils), all instruments are not currently supported and different instrument manufacturers need to be contacted for confirmation.


Precision and aperture


The precision of the sensor is to choose the very important indicators, can choose according to need, the precision is different, the price is different also, at the same time, it is important to note that if the test conductor coarser, you need to consider whether the aperture size appropriate, general sensor specification will have corresponding specifications, the proposal, as far as possible choose aperture connector wire thickness to ensure high precision of testing.


Ac/dc test


When selecting a sensor, it is important to note whether the sensor test signal is ac, dc or ac/dc. For example, many clamp sensors can only test ac signals, while roche coils can only test ac signals.


Temperature and delay


In the case of high temperature testing, attention must be paid to the temperature range of the sensor. Generally, the nominal precision of the sensor is 25℃ at room temperature, and the temperature fluctuation will affect the accuracy of the sensor.


In addition, the high frequency signal test, the influence on the precision of time delay, time delay difference is bigger, different types of sensor of hall sensor delay is greater than the roche coil delay, if there is a high frequency test requirements, can independence hall sensor calibration delay, PAH series rf power analyzer to support the input calibration instrument internal delays, effectively guarantee the test precision of the high frequency signal.