MODEL JH225: 2-WIRE TRANSMITTER
THERMOCOUPLE INPUT, USER-RANGEABLE, NONISOLATED

    • Thermocouple Types J, K and T
    • Input Ranges as Low as 2mV
    • Low-Drift Input Amplifier
    • Fits Standard Connection Heads
    • -40 to +80 Degree C Operation
    • DIN Rail mounting available

    JH225
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    DATA SHEET

    JH225
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    CAL INSERT

The Model JH225 2-wire transmitter provides a 4/20mA current loop output proportional to the input from a thermocouple. 16-position Zero and Span switches plus fine-adjust trimpots allow recalibration over a wide range of gains and offsets. Types J, K or T thermocouples may be selected. Cold junction compensation is located in the terminal block for optimum accuracy. Conformal coating protects the circuitry against condensation and corrosion in industrial atmospheres. Upscale burnout indication is standard.

The JH225 is a loop-powered device. Connected in series between a 24Vdc supply and readout instruments, it receives its power from the 4/20mA output loop. A built-in LED indicates loop current: dim at 4mA, bright at 20mA. The JH225 does not provide input/output isolation.

For a fixed range, factory-calibrated 2-wire thermocouple transmitter capable of handling all standard thermocouple types see Model JH220.

ORDERING INFORMATION

Model Number: 

Model JH225.

Input Range: 

The JH225 is normally shipped tested but uncalibrated. If you would like us to calibrate it simply specify on your order. We’ll do so at no extra charge. Specify thermocouple type J, K or T and specify any input range allowed by the "Input Capabilities" spec, below.

T/C Burnout Indication:  

(Always upscale – offscale high.)

Output Range: 

(Always 4/20mAdc.)

Power: 

(Always dc loop powered.)

DIN-Rail Mounting:  

Change model number to Model JH225-DIN. (See "Installation and Connections," below.)

INSTALLATION AND CONNECTIONS

The JH225 is 1-3/4 inches in diameter and is designed to fit many standard thermocouple-type connection heads. It may also be mounted to any surface using two #8 (or smaller) screws. An optional DIN-rail mounting clip (specify Model JH225-DIN) allows the transmitter to be snapped onto DIN rail. Width is 1-3/4 inches.

Connections are made to the transmitter’s terminal strip. Connections are:

"+" Terminal: Output/Power Loop. Receives current from (+) DC supply. 
"-" Terminal:
Output/Power Loop. Passes on current to the next series loop device, or to the (-) supply. 
Terminal A:
Thermocouple plus. 
Terminal B:
No connection – compensator is encapsulated in this position. 
Terminal C:
Thermocouple minus. (On most thermocouples, the red wire is minus.)

DETAILED SPECIFICATIONS

Input Capabilities:  

Span may be set anywhere from 2mV to 60mV. Low end (zero) may be set as follows: Type J, -210 to +340 deg. C. Type K, -270 to +520 deg. C. Type T, -270 to +400 deg. C.

Input Thermocouple Types:  

May be set for use with types J, K or T.

Thermocouple Burnout Indication:  

Output goes offscale high (above 20mA).

Output:  

4/20mA, 2-wire (loop-powered) output.

Accuracy (if properly calibrated)

+/-0.1% of span or 10 microvolts, whichever is greater.

Adjustability: 

Sufficient to achieve all specified input ranges.

Linearity: 

Linear with millivolts. Does not linearize the thermocouple.

Response Time: 

Under 100 milliseconds.

Guaranteed Operating Temperature: 

-40 to +80 deg. C (-40 to +176 deg. F).

Temperature Stability: 

+/-(0.02% of span plus 1 microvolt) per deg. C, or better.

Power Requirements: 

DC loop-powered. Requires at least 12Vdc at the transmitter’s output terminals. 36Vdc maximum.