Views: 0 Author: Site Editor Publish Time: 2022-07-15 Origin: Site
If the Rosemount transmitter is directly connected with a thermocouple or resistance temperature sensor, it may cause some problems at the input end of the host system of the instrument, thereby affecting the measurement effect of the transmitter.
To solve this problem, we can add a temperature transmitter near the sensor, such as:
1. Smart transmitters can collect and send data such as diagnosis and calibration.
2. Multiple transmitters can send data back through a single cable, and can also collect data from multiple sensors.
3. These smart transmitters can run for many years because they have built-in power modules and do not require other maintenance. There is an option to use a wireless HART protocol transmitter, which does not require the use of control system inputs or wiring.
4. No cables or input cards are required.
5. Using 4-20 mA current of digital protocols such as FOUNDATION fieldbus or HART, it can send a long distance and provide a relatively stable signal.
6. Most transmitters are compatible with a variety of resistance temperature detectors and thermocouples, so the sensor can be replaced when needed.
In order to monitor the temperature of the process fluid, the temperature transmitter uses thermocouples and thermal resistances as temperature measuring elements, and the output signal from the temperature measuring element is sent to the transmitter module, after voltage stabilization filtering, operational amplification, nonlinear correction, and V/I conversion, constant current and reverse protection and other circuits are processed, converted into a 4-20mA current signal 0-5V/0-10V voltage signal that has a linear relationship with temperature, and RS485 digital signal output. In various aspects, the present invention provides methods and apparatus for quickly and accurately determining the status of a temperature sensor, including confirming that a transmitter is properly connected to the temperature sensor. The temperature transmitter includes a measurement circuit operably connected to the at least one temperature sensor to provide an indication of an electrical parameter of the at least one temperature sensor.
A temperature transmitter is an instrument that converts a temperature variable into a transmittable, standardized output signal. Mainly used for the measurement and control of industrial process temperature parameters.
A temperature transmitter with a sensor usually consists of two parts: a sensor and a signal converter. Sensors are mainly thermocouples or thermal resistances; signal converters are mainly composed of measurement units, signal processing and conversion units (since industrial thermal resistances and thermocouple scales are standardized, signal converters are also called as independent products. Transmitter), some transmitters add display unit, and some also have fieldbus function. The temperature transmitter can be divided into two-wire system and four-wire system according to the power supply wiring mode, except that the RWB type temperature transmitter is a three-wire system.
Temperature transmitters include electric unit combination instrument series and miniaturized modular, multi-functional and intelligent types. The former do not have sensors, and the latter two types of transmitters can be easily combined with thermocouples or thermal resistances to form transmitters with sensors.
The power supply to the Rosemount Temperature Transmitter must not have spikes that could easily damage the transmitter. The calibration of the transmitter should be carried out 5 minutes after power-on, and pay attention to the ambient temperature at that time. When measuring high temperature (>>100°C), the sensor cavity and the junction box should be separated by filling material to prevent the junction box from being too high to burn out the transmitter. When using the sensor in the case of serious interference, the housing should be firmly grounded to avoid interference, the power supply and signal output should be transmitted by Ф10 shielded cable, and the crimping nut should be tightened to ensure air tightness. Only the RWB type temperature transmitter has 0~10mA output, which is a three-wire system. When it is below 5% of the range value, the non-linearity is caused by the turn-off characteristic of the triode. The temperature transmitter should be calibrated every 6 months. If the DWB cannot perform linear correction due to circuit limitations, it is best to select the range according to the instructions to ensure its linearity.