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The focus that 99% of us tend to overlook when choosing sensors

Release date:2019-12-10

In peacetime use of test and measurement equipment, due to the existence of the dc voltage test and measurement equipment, the current input value is restricted, in testing, usually used in sensors, for the selection of sensors, the top issue facing the under normal circumstances, we usually only care about sensor range 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 you select the appropriate sensors.


Whether the range of the sensor matches the measured signal, such as the current signal measured at 800A and the sensor measured at 1000A, but the signal output of the sensor also needs this range, which is the most important indicator and the most likely signal problem. In general, when choosing, we pay attention to the range suitable for the instrument itself. For example, the minimum range for PA5000H is 1A. The minimum display value of the current test instrument is 1.5% of the range, that is, the value below 15mA cannot be displayed. The sensor change rate is 1:1000. Therefore, it is appropriate to use PA5000H to equip 5A board CARDS at this time, since the minimum range of 5A board CARDS is 10mA and the output current value of sensors above 0.15ma can be displayed.


If a machine has been purchased, another solution is to use a patv-33 adapter that converts the sensor's current signal into a voltage signal and feeds it to the power analyzer's BNC port.


A, bandwidth


With instruments, sensors and same bandwidth parameters, especially the industry of 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 is determined by the lowest part of the testing system, such as 5 m bandwidth PA5000H 100 k bandwidth sensor, so the system bandwidth is 100 k, only in the test of high frequency and low frequency signals difference signal measurement, may be due to insufficient bandwidth test.


Sensor type


Current sensor, for example, generally 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, for example, are generally not portable sensors, high testing precision, output for current signals, such as lime, CT, LF series, bravely CTA series. This kind of sensor, at this moment just set corresponding scale in the instrument immediately can. A voltage current sensor is usually a BNC port, such as a current clamp, an oscilloscope current probe, etc., which converts a current signal into a voltage signal. At this point, the corresponding external sensor and rate of change should be set in the instrument. In addition, for special sensors with integrators (such as roche coils), not all instruments are currently supported, so we need to communicate and confirm with manufacturers of different instruments.



Three, precision and aperture


The precision of the sensor is to choose the very important indicators, can choose according to need, the precision of 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 specifications in the table will have corresponding specifications, the proposal, as far as possible choose aperture connector wire thickness to ensure high precision test.



Quad-ac-dc test



When selecting a sensor, you must pay attention to whether the sensor test signal is ac, dc or ac/dc. For example, many clamp sensors can only test ac signals, while the roche coil can only test ac signals.


Five, temperature and delay


In the case of high temperature testing, it is necessary to pay attention to the testing temperature range of the sensor. Typically, the nominal accuracy of the sensor is 25°c at room temperature. Temperature fluctuation will affect sensor accuracy.


In addition, the high frequency signal test, the impact on the precision of time delay is large, the different types of sensor delay difference is bigger, the time delay of hall sensor is greater than the delay time of roche coil, if you have high frequency test requirements, can be independently hall sensor calibration delay, PAH series rf power analyzer to support the input calibration instrument internal delays, effectively ensure the accuracy of the high frequency signal test.