Analysis of key points for sensor selection

How to choose a sensor? What are the key points to pay attention to? When using test and measurement equipment, due to the limited direct voltage and current input values ​​of the test and measurement equipment, sensors are often used during testing, and the selection of sensors becomes The first problem we face is that in normal times, we generally only care about whether the sensor's range meets the testing needs. But in addition, there are many points that need to be paid attention to when selecting sensors. This article takes the most commonly used current sensor as an example. Teach you step by step how to choose the right sensor.

Whether the range of the sensor matches the signal being measured. For example, if you measure an 800A current signal, choose a 1000A sensor, but the signal transferred out by the sensor must also be

Measuring range is the most important indicator, and it is also the place where problems are most likely to occur. Generally, when we choose, we will focus on the measuring range of the instrument itself. Take Laimzhi’s CTA1000 sensor with PA5000H and 50A power board as an example. The minimum range of PA5000H is 1A. The current minimum display value of the test instrument is 1.5% of the range. That is, values ​​below 15mA cannot be displayed. The sensor ratio It is 1:1000, and 1A current corresponds to a sensing output of 1mA, that is, currents below 15A cannot be displayed. Therefore, it is more appropriate to use PA5000H with a 5A board at this time, because the minimum range of the 5A board is 10mA, and sensor output current values ​​above 0.15mA can be displayed.

If the machine has been purchased, there are other solutions. It is equipped with a PATV-33 adapter, which can convert the sensor's current signal into a voltage signal and input it to the BNC port of the power analyzer.

1. Bandwidth

Like instruments, sensors also have bandwidth parameters. Especially in industries that measure high-frequency signals, such as motors, the efficiency often exceeds 1 or the efficiency is too low. Many of these situations are caused by insufficient sensor bandwidth. According to Cask Effect, the bandwidth of the entire test system is determined by the lowest part. For example, if the 5M bandwidth PA5000H is equipped with a 100K bandwidth sensor, then the system bandwidth is only 100K. There is not much difference when testing low-frequency signals. If high-frequency signals are measured, the bandwidth may vary. Insufficiency results in inaccurate testing.

2. Sensor type

For example, current sensors generally include voltage-type current sensors and current-type current sensors. The principles are different and the output signal types are also different. For example, most Hall sensors are generally closed sensors with high testing accuracy and output current signals, such as Lime CT, LF series, and Zhiyong's CTA series all belong to this type of sensor. At this time, just set the corresponding ratio in the instrument. Voltage current sensors generally have BNC ports, such as current clamps, oscilloscope current probes, etc., which convert the current signal into a voltage signal. At this time, the corresponding external sensor and transformation ratio need to be set in the instrument. In addition, for special sensors with integrators such as Rogowski coils, not all instruments currently support them. You need to confirm with the manufacturers of different instruments.

3. Accuracy and aperture

Accuracy is a very important indicator when selecting a sensor. You can choose according to your needs. Different accuracies have different price points. At the same time, it should be noted that if the test wire is thicker, you need to consider whether the aperture size is appropriate. Generally, the sensor specification table will have the corresponding Note, it is recommended to select the aperture to fit the wire thickness as much as possible to ensure high-precision testing.

4. AC and DC test

When selecting a sensor, you need to pay attention to whether the sensor test signal is AC, DC, or AC-DC. For example, many clamp sensors can only test AC signals, and Rogowski coils can only test AC signals.

5. Temperature and delay

When testing in high temperature situations, you need to pay attention to the test temperature range of the sensor. Generally, the nominal sensor accuracy is at room temperature of 25 degrees Celsius. Temperature fluctuations have an impact on the sensor accuracy. For different types of sensors, you need to consult the manufacturer specifically.

In addition, when performing high-frequency signal testing, delay has a great impact on accuracy. Different types of sensor delays vary greatly. The delay of Hall sensors is much larger than the delay of Rogowski coils. If there is a need for high-frequency testing, you can The Hall sensor performs separate delay calibration, and the PAH series power analyzer supports inputting the delay into the instrument for correction, effectively ensuring the accuracy of high-frequency signal testing. The above is an analysis of some key points in sensor selection. I hope it can help you.