SOME TIPS IN SENSOR AND INSTRUMENTATION

I recently participated in a project in which my part of job is to make instrumentation and data acquisition system. There are many lessons i gained from this experience, which i will share. in this blog, i will assume the sensor is electric sensor and has output such as analog voltage or digital data.

DON’T TRUST THE SENSOR

when you buy sensor, you will usually get datasheet or calibration sheet. you can use the sheet as reference, but it is much better if you check the sensor performance first, because there are many factor that can affect the sensor performance, such as tempereture, pressure, electromagnetic field and so on.

BACK TO PHYSICS

to check sensor performance, you can use high precision instruments on lab or create your own instrument by simple physics for several case, such water column for differential pressure, boiled water for 100 celcius degree temperature, ruler for distance and so on. by checking the sensor, you can determine whether you can use the sensor behaviour provided by the manufacturer or create the sensor behaviour formula based on the measured physical unit.

CALIBRATION FIRST

if you need to determine sensor behaviour by yourself, you can do it by taking data of physical unit measurement as sensor input and voltage as sensor output. more data is better. next step is to find the trend of your sensor behaviour. this will be clearer if you plot the data into graphic. in graphic form, you can easily determine the behaviour qualitatively such as linear, quadratic and so on. this can be done easily with microsoft excel. for further need, you can get trendline function from your graphic in excel.

DETERMINE SENSOR RANGE NEEDED

assuming you know the sensor behaviour, you need to choose sensor range you need to use. this can be done by evaluating extreme condition and resolution for measurement. this evaluation will be based on your design specification and need. you can use some sensor parallal connected to measure one quantity to improve extreme condition and resolution measurement. if you do this, you will probably need to find trendline of bahaviour for the two sensors to determine when you should use which sensor. another trick is to use zeroing method, that is to nullify the offset on sensor so you need to evaluate the change of sensor irrespective sensor offset

USE CABLE CONNECTOR

for better result, use cable connector. this will give you easy installation, neat look on your tool and reduce the possibility of loose connection. some connector will avoid wrong assembly and give good compatibility with other device.