Thermocouple measurement range is extensive and reasonable accuracy
Thermocouples have become the industry standard temperature temperature products, cost-effective range of measurement with a wide range of temperature and reasonable accuracy. They are widely used in a variety of applications in boilers, cement plants, power plants, oil fields and so on. The most popular thermocouple is a special material for thermocouples, made of iron and aluminum (registered trademark of nickel alloy containing chromium, aluminum, manganese, silicon, respectively), with a measuring range of 200 ° C to 1800 ° C.
Thermocouple measures connection type. Thermocouple signal conditioning should be designed to avoid grounded earthing thermocouple measurements, but there is also a path amplifier when the input bias current is measured by an insulated thermocouple. In addition, if the thermocouple head is grounded, the input range of the amplifier should be designed to handle any differences between the ground potential of the thermocouple and the measurement system on the ground. When grounding the selection, use a different type of prompt. For non-isolated systems, dual power supply signal conditioning systems are usually more powerful and exposed to the type. Due to its wide range of common-mode input, the dual power amplifier can handle a large number of voltage differences between the printed circuit board (printed circuit board) on the ground and the ground on the thermocouple head. A single power supply system can satisfactorily operate in all three cases if the common mode of the amplifier has a certain capability to measure the single power supply configuration below ground. To handle common mode limiting in some single supply systems, the bias voltage is useful for a scale thermocouple. This works as well as insulation thermocouple tips, or if the overall measurement system is isolated. However, this is not recommended for non-isolated systems for measuring ground or exposed thermocouples. Practical thermocouple solutions: Thermocouple signal conditioning is more complex than other temperature measurement systems. The time required to design and debug the signal conditioning can improve the time to market for the product. Incorrect signal conditioning, especially in the reference junction compensation section, can lead to low accuracy. The following solutions solve these problems. The first detail of a simple analog integrated hardware solution, combined with a direct thermocouple measurement reference junction compensation using a single integrated circuit. Scenario 2 Details Refer to the temperature compensation scheme for the software to provide more accurate thermocouple measurements and flexible use of multiple types of thermocouples. Measurement solution: Optimized for simple display of measuring K-type thermocouples. It is based on the use of the ad8495 thermocouple amplifier, which is designed for measuring K-type thermocouples. This analog solution is designed to optimize the minimum time: it has a simple signal chain and unwanted software coding. Measurement Solution 1: Optimization is simple. How does this simple signal chain address signal conditioning require K-type thermocouple? Gain and Output Scale Factor: Small thermocouple signal amplification ad8495 has a gain of 122, resulting in 5-mv / ° output signal sensitivity (200 ° /). Noise reduction: high frequency common mode and differential mode noise is caused by an external RF interference filter. The low frequency common mode noise is rejected by the ad8495 instrumentation amplifier. Any residual noise is made by an external post-filter. Reference junction compensation: In ad8495, which includes a temperature sensor to compensate for changes in ambient temperature, must be placed in the vicinity of the reference connection to keep the reference temperature compensation at the same temperature for accurate reference. Non-linear correction of the ad8495 calibration: 5 ° C / ° output of the linear part of the K-type thermocouple wire, less than 2 ° C linearity error in the temperature range of 25 ° C to + 400 ° C. If the temperature exceeds this range, the analog device application notes an-1087 describes how to look up the table or equation can be used in the microprocessor extended temperature range.
