C21 – 50x26mm Electronic Temperature Controller

Name: C21
SKU: C21
Availability: InStock

Low cost process and temperature controller.

C21 Features

Bright 4-digit LED with easy-to-read display
High-accuracy 18-bit A/D input resolution
Supports thermocouples & RTD (PT100) input
High-accuracy 18-bit A/D input resolution
Fast 5 samples/sec A/D conversion rate
2A relay or SSR voltage output selectable
Programmable ramping and dwell time
Auto/manual mode with bumpless transfer
Wide-range alarms: high, low, band, dwell
Lockout security with multiple access levels
RS-485/232 communication + PC setup port
CE, UL, CSA approvals with NEMA 4X / IP65 panel

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C21 Temperature Controller | Compact PID Control

The BrainChild C21 Temperature Controller is a 1/32 DIN compact PID controller designed for precise thermal process management in space-limited industrial applications. Featuring auto-tuning fuzzy logic, it adapts dynamically to process changes while maintaining stable and accurate temperature control.

With a bright 4-digit LED display, fast 18-bit A/D conversion, and options for relay or SSR output, the C21 provides the ideal balance of performance and size. It also supports RS-232/485 communication and comes with multiple alarm configurations and soft-start ramping to ensure reliable, secure operation.

Panel Interface｜LED Display with 3-Key Control

The C21 temperature controller features a compact and efficient front panel interface built for simplicity and ease of use. At the center is a bright 4-digit red LED display, offering clear visibility of current process values and setpoints even in dim environments.

Below the display are three responsive silicone rubber keys designed for quick navigation, parameter setting, and control mode switching. The tactile feel ensures reliable feedback during setup or runtime adjustment, minimizing errors in industrial conditions.

The compact layout fits standard 1/32 DIN panel cut outs, making the C21 ideal for space-constrained equipment while maintaining full functionality and safety visibility.

Input Specs｜Universal Thermocouple & RTD

The C21 temperature controller accepts a wide range of universal input signals, including thermocouples (J, K, T, E, N, R, S) and RTDs (PT100 DIN/JIS). It also supports analogue signals such as 0–50 mV, 0–20 mA, 4–20 mA, with flexible scaling and cold junction compensation. A high-resolution 18-bit A/D converter ensures accurate process monitoring, while a fast 5 samples/second sampling rate provides responsive control for dynamic applications. The input circuit features built-in sensor break detection for added safety.

Output Options｜Relay, SSR & Analogue Ready

The C21 offers flexible output configurations to meet various control needs. Depending on model and settings, users can choose from:

Relay contact output: rated 2A/240VAC for on/off control
SSR drive voltage output: for external solid-state relay triggering
Analog retransmission output: 0–20 mA, 4–20 mA, 0–10V with 15-bit D/A resolution

This output flexibility makes the C21 ideal for use in heating, cooling, or alarm control applications. Each output channel can be assigned to control, alarm, or retransmission functions based on system setup.

Power

90 – 250 VAC, 47 – 63 Hz, 10VA, 5W maximum

111 – 26 VAC / VDC, SELV, Limited Energy, 10VA, 5W maximum

Input 1	Characteristics
Resolution	18 bits
Sampling Rate	5 times / second
Maximum Rating	-2 VDC minimum, 12 VDC maximum ( 1 minute for mA input )
Temperature Effect	±1.5 uV/ °C for all inputs except mA input ±3.0 uV/ °C for mA input
Sensor Lead Resistance Effect	T/C: 0.2uV/ohm 3-wire RTD: 2.6 °C/ohm of resistance difference of two leads 2-wire RTD: 2.6 °C/ohm of resistance sum of two leads 200nA
Common Mode Rejection Ratio ( CMRR )	120dB
Normal Mode Rejection Ratio ( NMRR )	55dB
Sensor Break Detection	Sensor open for TC, RTD and mV inputs, Sensor short for RTD input, below 1 mA for 4-20 mA input, below 0.25V for 1 – 5 V input, unavailable for other inputs.
Sensor Break Responding Time	Within 4 seconds for TC, RTD and mV inputs, 0.1 second for 4-20 mA and 1 – 5 V inputs.

TYPE	Range	Accuracy@25°C	Input Impedance
J	-120°C -1000°C (-184°F -1832°F)	±2°C	2.2MΩ
K	-200°C -1370°C (-328°F -2498°F)	±2°C	2.2MΩ
T	-250°C -400°C (-418°F -752°F)	±2°C	2.2MΩ
E	-100°C -900°C (-148°F -1652°F)	±2°C	2.2MΩ
B	0°C -1820°C (32°F -3308°F)	±2°C (200°C – 1820°C)	2.2MΩ
R	0°C-1767.8°C (32°F -3214°F)	±2°C	2.2MΩ
S	0°C -1767.8°C (32°F -3214°F)	±2°C	2.2MΩ
N	-250°C -1300°C (-418°F -2372°F)	±2°C	2.2MΩ
L	-200°C -900°C (-328°F -1652°F)	±2°C	2.2MΩ
PT100 (DIN)	-210°C -700°C (-346°F -1292°F)	±0.4°C	1.3KΩ
PT100 (JIS)	-200°C -600°C (-328°F -1112°F)	±0.4°C	1.3KΩ
mV	-8mV -70mV	±0.05%	2.2MΩ
mA	-3mA -27mA	±0.05%	70.5Ω
V	-1.3V-11.5V	±0.05%	302KΩ

Output 1 / Output 2
Relay Rating	2A/240 VAC, life cycles 200,000 for resistive load
Pulsed Voltage	Source Voltage 5V, current limiting resistance 66

Linear Output Characteristics
Type	Zero Tolerance	Span Tolerance	Load Capacity
4-20 mA	3.6-4 mA	20-21 mA	500Ω max.
0-20 mA	0 mA	20-21 mA	500Ω max.
0-5 V	0 V	5-5.25 V	10KΩ min.
1-5 V	0.9-1 V	5-5.25 V	10KΩ min.
0-10 V	0 V	10-10.5 V	10KΩ min.

Linear Output
Resolution	15 bits
Output Regulation	0.01 % for full load change
Output Settling Time	0.1 sec. ( stable to 99.9 % )
Isolation Breakdown Voltage	1000VAC
Temperature Effect	±0.0025 % of SPAN / °C

Triac ( SSR ) Output
Rating	1A / 240 VAC
Inrush Current	20A for 1 cycle
Min. Load Current	50 mA rms
Max. Off-state Leakage	3 mA rms
Max. On-state Voltage	1.5V rms
Insulation Resistance	1000 Mohms min. at 500 VDC
Dielectric Strength	2500 VAC for 1 minute

Alarm ( Output 2 )
Alarm Functions	Dwell timer, Deviation High / Low Alarm, Deviation Band High / Low Alarm Process High / Low Alarm
Alarm 1 Relay	Form A,Max. rating 2A/240VAC, life cycles 200,000 for resistive load.
Alarm Mode	Normal, Latching, Hold, Latching / Hold.
Dwell Timer	0.1 – 4553.6 minutes

Data Communication
Interface	RS-232 ( 1 unit ), RS-485 ( up to 247 units )
Protocol	Modbus Protocol RTU mode
Address	1 – 247
Baud Rate	0.3 ~ 38.4 Kbits/sec
Data Bits	7 or 8 bits
Parity Bit	None, Even or Odd
Stop Bit	1 or 2 bits
Communication Buffer	50 bytes

Analog Retransmission
Output Signal	4-20 mA, 0-20 mA, 0-1V, 0-5V, 1-5V, 0-10V
Resolution	15 bits
Accuracy	±0.05 % of span ±0.0025 %/ °C
Load Resistance	0 – 500 ohms ( for current output ),10 K ohm minimum ( for voltage output )
Output Regulation	0.01 % for full load change

User Interface
Single 4-digit LED Displays	10mm (C21, C91)
Keypad	3 keys(C21), 4 keys(C91)
Programming Port	For automatic setup, calibration and testing
Communication Port	Connection to PC for supervisory control

Control Mode
Output 1	Reverse ( heating ) or direct ( cooling )action
Output 2	PID cooling control, cooling P band 50 ~ 300% of PB, dead band -36.0 ~ 36.0% of PB
ON-OFF	0.1 – 90.0 ( °F ) hysteresis control ( P band = 0 )
P or PD	0 – 100.0 % offset adjustment
PID	Fuzzy logic modified , Proportional band 0 ~ 500.0 °C , Integral time 0 – 1000 seconds , Derivative time 0 – 360.0 seconds
Cycle Time	0.1 – 100.0 seconds
Manual Control	Heat (MV1) and Cool (MV2)
Auto-tuning	Cold start and warm start
Failure Mode	Auto-transfer to manual mode while sensor break or A-D converter damage
Ramping Control	0 ~ 900.0°F/minute or 0 ~ 900.0 °F/hour ramp rate
Digital Filter	Function : First order Time Constant : 0, 0.2, 0.5, 1, 2, 5, 10, 20, 30, 60 seconds programmable

Environmental & Physical
Operating Temperature	-10°C ~ 50°C
Storage Temperature	-40°C ~ 60°C
Humidity	0 to 90 % RH ( non-condensing )
Insulation Resistance	20 Mohms min. ( at 500 VDC )
Dielectric Strength	2000 VAC, 50/60 Hz for 1 minute
Vibration Resistance	10 – 55 Hz, 10 m/s² for 2 hours
Shock Resistance	200 m/s2( 20 g )
Moldings	Flame retardant polycarbonate
Dimensions	C21 —50mm(W) X 26.5mm(H) X 110.5mm(D), 98.0 mm depth behind panel C91 —48mm(W) X 48mm(H) X 94mm(D), 86 mm depth behind panel
Mounting	C21 —panel mount, cutout 22 X 45( mm ) C91 —panel mount, cutout 45 X 45 ( mm )
Weight	C21 — 120 grams C91 — 140 grams
Altitude	2000m maximum

Approval Standards
Safety	UL 61010C-1 , CSA C22.2 No. 24-93 , EN61010-1 (IEC1010-1)
Protective Class	NEMA 4X ( IP65 ) front panel for C21, IP30 front panel for C91, all indoor use, IP20 housing and terminals
EMC	EN61326

C-21-(1)-(2)-(3)-(4)-(5)-(6)

1 Power Input	4: 90 - 250 VAC, 47-63 HZ
1 Power Input	5: 11 - 26 VAC or VDC, SELV, Limited Energy
2 Signal Input	1: Standard Input
	Thermocouple: J, K, T, E, B, R, S, N, L
	RTD: PT100 DIN, PT100 JIS
	2: 0 - 60 mV
	3: 0 - 1 V
	4: 0 - 5 V
	5: 1 - 5 V
	6: 4 - 20 mA
	7: 0 - 20 mA
	8: 0 - 10V
	9: Special Order
3 Output 1	0: None
	1: Relay rated 2A / 240VAC
	2: Pulsed voltage to drive SSR, 5V / 30mA
	3: Isolated 4 - 20mA / 0 - 20mA
	4: Isolated 1 - 5V / 0 - 5V
	5: Isolated 0 - 10V
	6: Triac output 1A / 240VAC,SSR
	C: Pulsed voltage to drive SSR, 14V/40mA
	9: Special order
4 Output 2	0: None
	1: Form A relay 2A / 240VAC
	2: Pulsed voltage to drive SSR, 5V / 30mA
	3: Isolated 4 - 20mA / 0 - 20mA
	4: Isolated 1 - 5V / 0 - 5V
	5: Isolated 0 - 10V
	6: Triac output, 1A / 240VAC, SSR
	7: Isolated 20V / 25mA transducer power supply
	8: Isolated 12V / 40mA transducer power supply
	9: Isolated 5V / 80mA transducer power supply
	A: RS-485 interface (for C91)
	C: Pulsed voltage to drive SSR, 14V/40mA
	D: Retransmit 4-20mA / 0-20mA (for C91)
	E: Retransmit 1-5V / 0-5V (for C91)
	F: Retransmit 0-10V (for C91)
	B: Special order
5 Communications	0: None
	1: RS-485 interface
	2: RS-232 interface(for C21)
	3: Retransmit 4 - 20 mA / 0 - 20 mA(for C21)
	4: Retransmit 1 - 5V / 0 - 5V(for C21)
	5: Retransmit 0 - 10V(for C21)
	9: Special order
6 Display Color	0: Red color
6 Display Color	1: Green color

Brainchild Low Cost Digital Controllers - Brochure 318.61 KB
Brainchild C21 Digital Controller - User Manual 981.95 KB

Product Range

Product Range:
Code	Specifications	Price
BTC-C21-411101	Digital Controller, 48 x 24mm, Standard input, Relay/Alarm, 90~250Vac	$289.00
BTC-C21-412101	Digital Controller, 48 x 24mm, Standard input, SSR/Alarm, 90~250Vac	$289.00
BTC-C21-413101	Digital Controller, 48 x 24mm, Standard input, 4~20mA/Alarm, 90~250Vac	$289.00
BTC-C21-511101	Digital Controller, 48 x 24mm, Standard input, Relay/Alarm, 11~26Vac/dc	$289.00

All prices are in NZ$, and GST exclusive and are subject to change without notice.

Intech Instruments Ltd are New Zealand distributors for Brainchild products. Please contact the Brainchild distributor in your country if you require sales or service support for Brainchild products.

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C21 Features

Usually in stock

C21 Temperature Controller | Compact PID Control

Panel Interface｜LED Display with 3-Key Control

Input Specs｜Universal Thermocouple & RTD

Output Options｜Relay, SSR & Analogue Ready

Product Range

Who we are

Intech Christchurch

Intech Auckland

Newsletter

C21 – 50x26mm Electronic Temperature Controller

C21 Features

Usually in stock

C21 Temperature Controller | Compact PID Control

Panel Interface｜LED Display with 3-Key Control

Input Specs｜Universal Thermocouple & RTD

Output Options｜Relay, SSR & Analogue Ready

Product Range

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Who we are

Intech Christchurch

Intech Auckland

Newsletter