Sensors & Measurements
Sensors can be used to measure almost anything, for a data logging system the input you are measuring will need to be converted into a digital value. This allows the values to be stored, processed and transferred through the rest of the system. Most commonly an Analogue to Digital Converter (ADC) will be used to acheive this, an ADC can convert a voltage into a digital value. In order to successfully use an ADC it is important to design the electronics carefully to ensure the system is designed with the most appropriate level of accuracy and dynamic range for the application.
For an ADC based measurement system to work, the input needs to first be converted to a voltage. Most off-the-shelf sensors for such things as humidity, torque, light reception etc. commonly result in a voltage that can be easily measured. A sensor that changes resistance can be used to generate a varying voltage and even a current can be converted into a measureable voltage.
A common requirement for a measurment or test system is to measure temperature. Normally this will use a thermocouple, for which there are several standard interface chips. A thermocouple works by making use of the seebeck effect; by connecting two different metals a small voltage is produced when a temperature difference is present. Specialist thermocouple conversion chips almost always convert the tiny voltages generated by the thermocouples into digital values representing the temperature. There are other temperature sensors that vary in resistance which you need to measure.
Dotstar design has experience working with many different types of sensor, using Analog to Digital converter (ADC) chips or specilist devices that are designed for a particular sensor. We have a lot of experience measuring very small signals and ensuring use of good design principals to reduce noise where possible increasing measurement accuracy. To read more about Dotstar Design's experience developing high performance ADC based designs click here.
Dotstar design have also worked with measuring higher level effects, such as the frequency or delay of a signal from a sensor. These still need a voltage to be measured, but then extra processing to be performed on a series of those measurements to generate the required information.
Some applications require more complex sensors - one of our customers has designed custom fibre optic probes that we interface to and we worked on developing a ultrasonic flow sensor for a particular application.
Once the sensor and measurement scheme has been selected normally this will need connecting to some form of embedded processor or FPGA. This will be able to control the measurement system, manage the rate of measurement, allow for further data processing and transfer of measurements either directly or indirectly to your computer.