Applications

It is usually used in conjunction with display instruments, recording instruments, electronic computers, etc., with a 4～20mA output. This product directly measures the temperature of liquid, steam, gas media and solid surfaces in the range of -200℃～1300℃ in various production processes.

Features

Two-wire system with 4～20mA output, featuring strong anti-interference ability;
Saves costs on compensation wires and temperature transmitter installation;
Wide measurement range;
Equipped with automatic cold junction temperature compensation and non-linear correction circuit.

Working Principle

The explosion-proof thermocouple adopts the gap explosion-proof principle. When an explosion occurs inside the cavity, the flame after the explosion can be extinguished and cooled through the joint surface gap, preventing the flame temperature from spreading outside the cavity, thereby achieving temperature measurement. The thermoelectromotive force (resistance) generated by the thermocouple (resistor) produces an unbalanced signal through the bridge of the temperature transmitter. After amplification, this signal is converted into a 4～20mA DC signal and transmitted to the working instrument, which then displays the corresponding temperature value.

Main Technical Parameters

Product Execution Standards

IEC584, IEC1515, IEC751, JB/T5518-91, JB/T7391-94

Temperature Measurement Range and Allowable Error

Thermocouple

Model	Index Number	Accuracy Class	Allowable Error	Temperature Measurement Range (℃)
WRNB	K	Class I	±1.5℃; ±0.004│t│	-40～+375; 375～1000
WRNB	K	Class II	±2.5℃; ±0.0075│t│	-40～+333; 333～1200
WRMB	N	Class I	±1.5℃; ±0.004│t│	-40～+375; 375～1000
WRMB	N	Class II	±2.5℃; ±0.0075│t│	-40～+333; 333～1200
WREB	E	Class I	±1.5℃; ±0.004│t│	-40～+375; 375～800
WREB	E	Class II	±1.5℃; ±0.004│t│	-40～+333; 333～900
WRFB	J	Class I	±1.5℃; ±0.004│t│	-40～+375; 375～750
WRFB	J	Class II	±1.5℃; ±0.004│t│	-40～+333; 333～750
WRCB	T	Class I	±1.5℃; ±0.004│t│	-40～+125; 125～350
WRCB	T	Class II	±1℃; ±0.0075│t│	-40～+333; 133～350
WRPB	S	Class I	±1℃; ±[1+0.003(t-1100)]	0～+1100; 1100～1600
WRPB	S	Class II	±2.5℃; ±0.0025│t│	0～600; 600～1600

Thermistor

Model	Index Number	Temperature Measurement Range (℃)	Accuracy Class	Allowable Error
WZPB	Pt100	-200～+500	Class A; Class B	±(0.15+0.002\|t\|); ±(0.30+0.006\|t\|)
WZCB	Cu50; Cu100	-50～+100	-	±(0.30+0.005\|t\|)

Note: t is the absolute value of the measured temperature of the temperature-sensitive element

Parameter Item	Specification Details
Output Signal	4～20mA, load resistance 250Ω, transmission wire resistance 100Ω
Output Method	Two-wire system
Accuracy Class	Temperature Transmitter: 0.1; 0.2; 0.5; Display: Analog indication 2.5 class; Digital display 1.0 class
Power Supply	24V.DC±10%
Protection Class	IP65
Explosion-proof Class	Explosion-proof type: dIIBT4, dIICT5, dIICT6; Intrinsically safe type: iaIICT6
Insulation Resistance	The insulation resistance between the instrument's output terminal and the housing shall not be less than 50MΩ
Thermal Response Time	When the temperature changes stepwise, the time required for the instrument's current output signal to change to 50% of the step change is usually expressed as τ0.5. If the step response stabilization time of the temperature transmitter does not exceed 1/5 of the thermal response stabilization time τ0.5 of the thermocouple (resistor), the thermal response time of the thermocouple (resistor) is used as the thermal response time of the instrument; If the step response stabilization time of the temperature transmitter does not exceed 1/2 of the thermal response stabilization time τ0.5 of the thermocouple (resistor), the thermal response time of the temperature transmitter is used as the thermal response time of the instrument.
Basic Error	The basic error of the instrument shall not exceed the combined error of the basic errors of the thermocouple (resistor) and the temperature transmitter

Working Environment

Installation Site Class	Temperature (℃)	Relative Humidity (%)	Atmospheric Pressure (KPa)
Cx1	-25～+55	5～95	86～106
Cx2	-25～+70	5～95	86～106
Cx3	-40～+80	5～95	86～106

Determination of Support Tube Length

The operating temperature of the temperature transmitter is the sum of the housing temperature rise caused by the support tube and the ambient temperature. The housing temperature rise caused by the support tube is shown in the figure below (note: figure not provided in original data).

Certification List

Explosion-Proof Class	Explosion-Proof Certificate No.	Certification Body
dⅡB T4	GYB97151	NEPSI (National Instrumentation Explosion-Proof Safety Supervision and Inspection Station)
dⅡB T4	GYB97152
dⅡC T4	GYB97203
dⅡB T5	GYB97204
iaⅡCT6	GYB99412
iaⅡCT6	GYB99413