Brainchild Safety L91 Limit Controller

 The limit control L91 is over-temperature protection or a high limit safety device with a latching output, that removes power in an abnormal condition during the process is higher than the high limit set point or lower than the low limit set point.

The unit is powered by 11-26 or 90-264 VDC/VAC supply, incorporating a 3 amp. form C relay for limit control, an universal input which is fully programmable for PT100, thermocouple types J,
K, T, E, B, R, S, N, L and 0~60mV, an option port available for one of the following functions: alarm output, RS-485 communication interface, DC power supply output, limit annunciator output and event input. Alternative output options include SSR drive and triac. The input signal is digitized by using an 18-bit A to D converter. Its fast sampling rate (5 times/second) allows the L91 to control fast processes such as pressure and flow.

Digital communication RS-485 is available as an additional option. This option allows L91 to be integrated with a supervisory control system. An alarm output is another option. A variety of alarm function and alarm mode can be programmed for a specific application. The DC power supply output option is used for an external sensor or transmitter. The event input option can be programmed for remote reset or remote lock signal input. The limit annunciator option can be used to control an alarm buzzer.

Thress kinds of method can be used to program L91.

  1. Use keys on front panel to program the unit manually,
  2. Use a PC and setup software to program the unit via RS-485 port and
  3. Use a pc and configuration software to program the unit via programming port.

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High accuracy, maximum flexibility, fast response and user-friendly are the main feature of L91



90 - 250 VAC, 47 - 63 Hz, 10VA, 5W maximum
11 - 26 VAC / VDC, SELV, Limited Energy, 10VA, 5W maximum

Signal Input

Signal InputCharacteristics
Resolution18 bits
Sampling Rate5 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 EffectT/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
Burn-out Current200nA
Sensor Break DetectionSensor open for TC, RTD and mV inputs,
below 1 mA for 4-20 mA input,
below 0.25V for 1 - 5 V input, unavailable for other inputs.
Sensor Break Responding TimeWithin 4 seconds for TC, RTD and mV inputs,
0.1 second for 4-20 mA and 1 - 5 V inputs.


TypeRange Accuracy@ 25 °CInput Impedance
J-120 ~ 1000 °C (-184 ~ 1832 °F)±2 °C2.2MΩ
K-200 ~ 1370 °C (-328 ~ 2498°F)±2 °C2.2MΩ
T-250 ~ 400°C (-418 ~ 752°F)±2 °C2.2MΩ
E-100 ~ 900 °C (-148 ~ 1652 °F)±2 °C2.2MΩ
B0 ~ 1800 °C (32 ~ 3272 °F)±2 °C (200°C - 1800°C)2.2MΩ
R0 ~ 1767.8 °C (32 ~ 3214 °F)±2 °C2.2MΩ
S0 ~ 1767.8 °C (32 ~ 3214 °F)±2 °C2.2MΩ
N-250 ~ 1300 °C (-418 ~ 2372 °F)±2 °C2.2MΩ
L-200 ~ 900 °C (-328 ~ 1652 °F)±2 °C2.2MΩ
PT100 (DIN)-210 ~ 700 °C (-346 ~ 1292 °F)±0.4°C1.3KΩ
PT100 (JIS)-200 ~ 600 °C (-328 ~ 1112 °F)±0.4°C1.3KΩ
mV-8 ~ 70mV±0.05%2.2MΩ
mA-3 ~ 27mA±0.05%70.5Ω
V-1.3 ~ 11.5V±0.05%650KΩ

Input 2

Resolution18 bits
Sampling Rate1.66 times / second
Maximum Rating-2 VDC minimum, 12 VDC maximum
Emperature Effect±1.5uV/ °C for all inputs except mA
input ±3.0uV/ °C for mA input
Common Mode Rejection Ratio ( CMRR )120dB
Normal Mode Rejection Ratio ( NMRR )55dB
Sensor Break DetectionBelow 1 mA for 4-20 mA input,
below 0.25V for 1 - 5V input,
unavailable for other inputs.
Sensor Break Responding Time0.5 second


Output 1 / Output 2
Relay Rating2A/240 VAC, life cycles 200,000 for resistive load
Pulsed VoltageSource Voltage 5V, current limiting resistance 66Ω


Triac ( SSR ) Output
Rating1A / 240 VAC
Inrush Current20A for 1 cycle
Min. Load Current50 mA rms
Max. Off-state Leakage3 mA rms
Max. On-state Voltage1.5V rms
Insulation Resistance1000 Mohms min. at 500 VDC
Dielectric Strength2500 VAC for 1 minute


DC Voltage Supply Characteristics ( Installed at Output 2 )
TypeToleranceMax. Output Current Ripple VoltageIsolation Barrier
20V±1 V25 mA0.2 Vp-p500 VAC
12V±0.6 V40 mA0.1 Vp-p500 VAC
5V±0.25 V80 mA0.05 Vp-p500 VAC

Data Communication

Data Communication
InterfaceRS-232 ( 1 unit ), RS-485 ( up to 247 units )
ProtocolModbus Protocol RTU mode
Address1 - 247
Baud Rate0.3 ~ 38.4 Kbits/sec
Data Bits8 bits
Parity BitNone, Even or Odd
Stop Bit1 or 2 bits
Communication Buffer50 bytes


User InterfaceDual 4-digit LED Displays
Keypad4 keys
Programming PortFor automatic setup, calibration, and testing
Communication PortConnection to PC for supervisory control

Limit Control

High Limit, Low Limit and High/Low Limit programmable

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
Humidity0 to 90 % RH ( non-condensing )
Altitude2000m maximum
PollutionDegree 2
Insulation Resistance20 Mohms min. ( at 500 VDC )
Dielectric Strength2000 VAC, 50/60 Hz for 1 minute
Vibration Resistance10 - 55 Hz, 10 m/s² for 2 hours
Shock Resistance200 m/s2( 20 g )
MoldingsFlame retardant polycarbonate
Dimensions96mm(W) X 96mm(H) X 65mm(D), 53 mm depth behind panel
Mounting48mm(W) X 48mm(H) X 94mm(D), 86 mm depth behind panel
Weight150 grams

Approval Standards

SafetyFM Class 3545 (Oct. 1998), UL873 ( 11'th edition, 1994 ) , CSA C22.2 No. 24-93 , EN61010-1 (IEC1010-1)
Protective ClassIP30 front panel, indoor use,
IP20 housing and terminals ( with protective cover)