1、 Overview:
AT303 is a temperature transmitter designed to accept standard platinum resistors (Pt100 two wire or three wire), which complies with BS1904 or DIN43760 standards and converts temperature into industry standard 4-20mA current. The transmitter is packaged in a DIN standard connection module. There are three standard factory calibration ranges for transmitters. There is a fine adjustment potentiometer in the module, which is used for final zero calibration and range adjustment. The material is 316L stainless steel, suitable for use in the pharmaceutical and food industries.
The wiring method for 4-20mA loop current output is shown in Figure 1. The Pt100 sensor shown in the figure is usually provided in the form of a three wire probe assembly. The output loop represents a 24V DC power supply for sensors, transmitters, and loads connected in series. The load RL represents other devices in the loop, usually indicators, controllers, recorders, etc. Sometimes, these devices come with a built-in 24V DC power supply as a standard component to simplify wiring and reduce costs. When designing a 4-20mA circuit, attention should be paid to ensuring the overall load-bearing capacity of the loop, that is, the total voltage required by various devices in the loop should not exceed the power supply voltage value. If several instruments are connected in the loop, it should be ensured that only one instrument is grounded. If two points are grounded, it will cause a short circuit in one of the instruments between these two points, making it unable to operate.
2、 Technical indicators(At an ambient temperature of 20 ℃)
Input: Pt100 sensor complies with BS1904 standard or DIN4376 standard
Output: 4-20mA, maximum 30mA
Power supply voltage: 11-32VDC
Loop resistance: 700 Ω at 24VDC
Loop protection: Reverse polarity protection
Loop sensitivity: 10 μ A/V
Accuracy: ± 0.5% FS
Temperature stability: The typical zero drift value is 0.05%/℃
The typical range drift value is 0.002%/℃
Environmental temperature: 0-50 ℃
Storage temperature: -40~70 ℃
Environmental humidity: 0-95%, no condensation
Material: 316L stainless steel
Cable size: It is recommended that the maximum cable area be 2.5mm2

3、 External dimensions:

4、 Product selection

5、 Installation
The transmitter is installed using two mounting holes with a diameter of 5.5mm and a center distance of standard 33mm. The transmitter is specifically designed to be installed inside the DIN beam probe housing, which should have appropriate moisture-proof and anti-corrosion protection. All incoming cables must be of appropriate size and sealed.
6、 Electrical connection

The wiring of the transmitter is connected to the threaded terminal at the top of the transmitter. There are no special requirements for output wiring, but it is best to use twisted pair cables for long-distance cables. It is recommended to use three core shielded cables for input signal lines. The three core input lines should have the same cross-sectional area to maintain the same resistance for each wire. There is a sensor in the transmitter that passes through the transmitter housing and is directly connected to the threaded terminal block. Threaded terminals are specifically designed for connecting internal and external input and output lines.
The transmitter uses a series diode as reverse protection. When the power supply is connected incorrectly, the transmitter has no current; When the sensor input line is connected incorrectly, working together will cause the transmitter to saturate the high and low limits.
(Warning: The power supply voltage should not exceed the specified rated value, and AC power supply should not be used.)
To verify the transmitter range, the following steps can be used for calibration:
1. Use three wires to connect a precision resistance box (or Pt100 calibrator) to the transmitter, replacing the Pt100 temperature sensor. The output terminal of the transmitter is connected in series with an ammeter to a 24V DC power supply. The accuracy of the resistance box is 0.01R, and the accuracy of the ammeter is equal to 0.05% FS. Connect the power supply.
2. Refer to the Pt100 table and set the resistance value of the resistance box to the equivalent resistance value of the sensor at 4mA (temperature zero point). Adjust the zero point (z) potentiometer to make the transmitter output 4mA - ± 0.01mA.
3. Refer to the Pt100 table and set the resistance value of the resistance box to the equivalent resistance value of the sensor when the output is 20mA (full temperature). Adjust the range (S) potentiometer to make the transmitter output 20mA.
4. Repeat steps 2-3 until the two points are aligned. Note that there is some mutual influence between zero point and range adjustment.
5. Turn off the power and remove the connecting wires.
7、 Maintenance
After installation, the AT303 temperature transmitter does not require daily maintenance. The transmitter cannot be repaired on site. If it needs to be repaired, please send the transmitter back to our company and attach the fault and application information.

• AT303 sanitary temperature transmitter. pdf