HOW TO CHOOSE THE RIGHT SENSORS FOR YOUR SYSTEM?
Practical tips and simple technical overview for consideration in choosing the right sensor.
It is very important to choose the right sensor for your system to ensure the smoothness of operation and maintenance also sustainability in the long term period. You must have a deep understanding of how your system work, its characteristics, the configuration also the function of each device on your system. The following consideration is important to choose the right sensor.
Range of sensor
Make sure that you get accurate data of maximum and minimum values that need to be measured. Better to add safety factors for your range. For example, for measuring water level, you need to know the historical Highest Water Level (HWL) and Lowest water level (LWL) at the location where you will build Water Level Monitoring Station. It can be based on a study or field survey by asking local people about the biggest flood and the maximum level.
Needed Range of the sensor = (HWL -LWL) *SF
SF = safety factor, to anticipate the bigger range which possible will happen in the future.
If the range is less than the needs, (you need a 10 m water level range, but you buy a 5-meter range) you won’t get the data if the water level is more than 5 meters. This is a big mistake because it will be possible you will not get an alarm for the critical level.
If the range is much bigger than the needs, you will have a higher error tolerance (accuracy). for example, you need a 10 m sensor range, but you buy a 100 m sensor range, the allowed error tolerance let say 0,3% from full scale (FS). For 100 m, accuracy = 0.003*100 =0,3 m or 30 cm while for 10 m, accuracy = 0.003*10 m= 3 cm.
If the range is only 10 m, you buy 100 m sensor range, the possible maximum deviation is 30 cm.
Resolution
The resolution’s smallest possible reading unit which can be detected by the sensor. For example, Rainfall tipping bucket. If you need to measure the very low rain intensity where very light rain can be detected, you need to buy a 0.1 mm tipping bucket. Or if you need to measure 0.1 C temperature, you need 0.1 C resolution for the sensor. Better resolution means the more expensive you have to spend.
If you choose a bigger resolution sensor than the needs, you will not be able to detect the changing of parameters in the needed resolution. On the other hand, if the resolution is less than the needs, it will be better, but you must spend more money.
Working Temperature
You must know the environment of the sensor, the minimum temperature, and the maximum possible temperature. Make sure the range of temperature is wider than the needs.
If the range is less than the needs, in a certain situation your sensor will not be operating properly. If the sensor range is 0-100 C while the environment is 120 C, you won’t get the data when the temperature is above 100 C. If the range is too wider, you need a 0-100 sensor range but you buy -30 C - 100 C, the sensor is will never work in less than 0 C, it is mean not efficient also you will pay a higher price.
The output of the sensor
Check the interface of the device which will be connected, such as Datalogger, PC, Controller. The available input for the device must be available on the sensor output. For example, if the data logger requires 4-20 mA input, make sure your sensor output is also 4-20 mA. You cannot connect RS485 sensor output to 4-20 mA device input directly.
choose the sensor with needed output only, plus possible output which possibly will be used in the near future. Don’t choose sensor with too many output where you will never use it.
Consider the distance between the sensor transducer and connected device, the characteristic of each output will be different, make sure the needed distance is within the range.
Method of measurement
Collect information about the environment where your sensor will be installed. The available space, environtment risk, technical precondition, and specifict requirement. For example, you need to measure waterflow in pipe without pressure drop, you can not choose electromagnetic type, you need ultrasonic clamp where the tranducer is not inserted inside the pipe.
if we know how sensor works, the sensor can adapt to the spesific charasteristic of location also your technical requirement.
IP Protection
Ingress protection (IP) used to rate the degree of protection or sealing effectiveness in electrical enclosures against intrusion of objects, water, dust or accidental contact. Make sure you choose the right choice according to the environment risk where your sensor will be located.
You don’t need to buy sensor with IP 67 that mean dust proof and can be submerged within 15 cm up to 1 m depth for clean and free water location.
Budget
Make sure the price within allocated budget. If after evaluation based on above explanation you need more than allocated, consider to add the budget.
After sales and technical support
Make sure the sensor has adequate technical support and good after sales service to support your operation and maintenance in the future.
I hope above explanation will help you on to choose the best sensor for your system.
Good luck!