General description
XTRM Series Remote Temperature Monitors are multi-point temperature measurement instrument. It takes the highest measured temperature in the measuring loops as its output signal which is sent out in the form of 4-20 mA standard current signal and the temperature is indicated by the built-in display. If required, temperature at any measuring points can also be shown by operating the keys on the panel.
This temperature monitor is mainly used in applications of multi-point temperature measurement or alarm system. By using advanced technology such as SMT process, the instrument offers excellent accuracy and reliability, and protection against interference at production site.
The series instruments are available with 2, 3, 4 , 5 and 6 measuring loops.
Technical specifications
Measuring range           0~100ºC,0~150ºC,0~200ºC
(According to user's demand)
Input type                Pt100, Cu50 (TC if specially required)
Measuring Points          2, 3,4,5,6 points
Convert accuracy          ≤0.5%
Linearity error             < 0.1%
Output                   4~20mA  Electrical isolation output
Digital display             LED
Display accuracy           0.5%
Voltage drop for display      3V
Isolated voltage Drop        2V
Isolate Voltage             1500V AC (Input/output,with isolator)
Max-load                (V -14V~16V)/0.025A (Current output)
Limit current              ≤25mA
Response time             1s
Power supply              14…16~30V DC
Temperature drift          0.025% FS/ 1ºC
Long-term stability         ≤0.1ºCper year or 0.05% per year
Ambient                 -40~+85ºC (Aluminum alloy Casing)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
-25 ~+75ºC(Plastic Casing)
Degree of protection        IP66 (Aluminum alloy)/IP62(Plastic)
Anti-RFI                >10v/m(80MHz...1000MHz)
Wiring diagram    (4-point for example)

Electrical connection    (4-point for example)
The instrument cover need to be opened in order to make electrical connection to the resistance thermometer sensors. Input and output terminals are on the base plate below.


Structure and dimension (in mm)

Aluminum alloy casing
Installation
Aluminum alloy casing


Vertical conduit

Horizontal conduit
Principle of operation
XTRM Series remote temperature monitor is a signal converter with multi-point inputs and one output of 4 to 20 m A which is also the power supply of the instrument as well, and shall be installed close to the measuring point. See Fig.1 (take Pt100 four-loop, input range 0-150 ºC as an example)
The output current is comprised of a constant current of 4 m A that acts as both zero point and power supply of the instrument, and a varying current of 0 to 16 m A that directly proportional to the variation of measuring input signal, for which input of 0 to 150ºC corresponding to output of 4 to 20 m A. Signals from resistance thermometer sensors are amplified by preamplifiers, and selected by input comparing circuit(to select the highest temperature signal) or by measuring point selecting circuit to select the measuring loop. The selected signal is then converted by voltage/current (V/I) converting element from the output voltage of preamplifier into 4 to 20 mA constant current output. See Fig.2.
    
Application
1. The instrument needs 10 minutes to warm up after power turn-on.
It is advisable that the instrument be mounted as nearer to the measuring point as possible, so as to make good use of the advantages of the two-wire system:
  a. High ability of resistance against interference: as signals are transferred in high level, noise and interference can be effectively restrained.
  b. Easier wiring: the instrument can be wired to the control room with only a twisted pair,
resulting in reduction of wiring cost.
2. To avoid measuring error, the resistance of connecting wire shall be kept constant at 0.35Ω. Otherwise, deviation of every 0.38Ω in wire resistance will cause an error of 1ºC in measurement.
The magnitude of load resistance RL depends upon several factors such as indication model, supply voltage Vs, voltage ripple Vr and adoption of input/output isolation.
For LED digital type:
                    
For LED digital (isolation) type:
                    
If Vs=24V, Vr =2Vpp, it is concluded that RL= 550Ω (LED digital type), RL=400Ω(LED digital isolation type).
3. For those not currently in use loops, connect a 100Ω(or smaller) resistance or a simple wire to short circuit the input terminal. The instrument can't work properly with open loops.
4. Under normal working conditions, the instrument measures temperature at multi-points simultaneously, but only takes the highest measured temperature as its output signal..
Maintenance and adjustment
No special maintenance is needed during normal operation, owing to the feature of durability test and factory aging calibration. We guarantee lifetime repair or maintenance for any of our instrument.

If the output current exceeds 20mA and the instrument cannot work properly. In most cases, it is caused by open loop of the sensor, or decrease of isolation resistance between the sensor and protection sleeve (No such error ever found in isolation type).
If there is an input short circuit in a loop, the instrument can still work. As you select the loop, the output current is lower than 4 mA, and the indication should be read less than zero.
Instrument adjustment procedures:
Periodic calibration of the instrument can be carried out in accordance with the following procedures (take Pt100 four-loop, input range 0-150 ºC as an example):
1. Open the instrument cover and power on. Connect a standard resistance to the first loop input terminal, tune to 100Ω. Short circuit all other input terminals.
2. See Fig 5, adjust potentiometer W11 so that the output reaches 4 m A. With the input resistance reaches 157.3Ω, adjust W12 so that the output reaches 20 m A. Repeat the above steps several times until satisfactory accuracy is obtained.
3. Connect standard resistance box to the second loop, using above step 2 to adjust potentiometers W21 and W22 until outputs reach 4 m A and 20 m A respectively. When adjusting the second loop, short circuit all other input loops.
4. Connect standard resistance box to the third and fourth loops to repeat the above step 2. Adjust in turn W31, W32, W41 and W42 until all four loops adjustment completed (Short circuit the loops not currently in adjustment).
                    
Ordering code