Watlow Series L Temperature Limiting Controller

(1) Power supply parameters

Series power supply voltage range, frequency, power consumption, power-off data storage

LF/LV 24V AC（+10%/-15%）、120V AC（+10%/-15%）、230-240V AC（+10%/-15%） 50/60Hz ± 5% maximum 10VA non-volatile memory (parameters not lost)

LS 100-240V AC (+10%/-15%) 50/60Hz ± 5% maximum 10VA non-volatile memory

(2) Environmental parameters

Working environment: Temperature 0-70 ° C (32-158 ° F), relative humidity 0-90% RH (non condensing), avoid direct contact of condensed water with equipment.

Storage environment: Temperature -40-85 ° C (-40-185 ° F), relative humidity 0-95% RH (non condensing).

Anti interference capability: Complies with EN 61326-1 standard, industrial environment anti electromagnetic interference (EMI), sensor cables are recommended to use shielded wires (only grounded at the sensor end), away from high-voltage power lines (spacing ≥ 10cm).

3. Sensor and input specifications

(1) Thermocouple input

Thermocouple Type Range (Example) Accuracy Key Requirements

E-type -200-800 ° C (-328-1470 ° F) ± 1% range ± 1 ° C (standard conditions 25 ° C ± 3 ° C) needs to distinguish between positive and negative poles (red is negative), and extension requires the same type of compensating wire to avoid errors caused by copper wires

J-type 0-750 ° C (32-1382 ° F); LS series: -18-406 ° C (0-763 ° F) ± 1% range ± 1 ° C Suitable for medium and low temperature scenarios, low cost, good oxidation resistance

K-type -270-1370 ° C (-328-2282 ° F); LS series: -18-537 ° C (0-999 ° F) ± 1% range ± 1 ° C Suitable for high temperature scenarios, good stability, widely used in industrial furnaces and kilns

T-type -200-350 ° C (-328-662 ° F) ± 2.4% range (-200-0 ° C), ± 1% range (0-350 ° C) suitable for low temperature scenarios (such as refrigeration equipment), resistant to humidity corrosion

Input impedance:>10M Ω, to avoid errors caused by external circuit shunting; Cold end compensation: Built in electronic cold end compensation with an accuracy of ± 0.1 ° C, without the need for additional compensation wires.

(2) RTD input (only supported by LF/LV)

Type: 100 Ω platinum resistor, in accordance with DIN 0.00385 temperature coefficient curve.

Range: -200-800 ° C (-328-1472 ° F).

Wiring method:

3-wire system: S1 (signal+), S2 (signal -), S3 (compensation), automatically compensates for wire resistance.

2-wire system: S2 and S3 terminals need to be short circuited. For every 1 Ω increase in wire resistance, the measurement error increases by 2.6 ° C (4.7 ° F). It is recommended that the wire length be ≤ 10 meters.

Excitation current: 125 µ A (nominal), to avoid excessive current causing RTD self heating error.

4. Output and protection specifications

(1) Output type and parameters

Series output types, rated parameters, applicable load life

LF/LV Form C mechanical relay (single pole double throw) 8A/240V AC (resistive load), 250VA (inductive load, 120/240V AC), 30V DC (maximum) contactor coil, solenoid valve, alarm light, etc. Inductive load requires parallel RC suppressor (Watlow P/N 08040147-0000) 100000 cycles (at rated current)

LS Form A mechanical relay (single pole single throw) 8A/240V AC (resistive load), 120VA (inductive load, 120/240V AC) is only used to cut off high-risk loads (such as heating tube power supply), without the need for RC suppressors for 6000 cycles (at rated current)

Output logic: Under normal conditions, the NO (normally open) contact of LF/LV is closed and the NC (normally closed) contact is open; After triggering the restriction condition, the output is locked, the NO contact is disconnected, and the NC contact is closed (cutting off the load power or triggering an alarm).

(2) Protection function

Temperature limit:

High temperature limit (full series): Protection is triggered when the temperature exceeds the set point.

Low temperature limit (LF/LV only): Protection is triggered when the temperature is below the set point (such as freezing of refrigeration equipment).

Sensor fault protection:

Sensor open circuit: triggers output lockout, displays fault code [Er; In] (only LV is displayed).

Sensor short circuit: When the thermocouple is short circuited, the ambient temperature is displayed, and when the RTD is short circuited, the low range value is displayed, both triggering protection.

LS series additional protection:

Dual sensor deviation monitoring: When the temperature difference between the two sensors exceeds 20 ° C, protection is triggered to prevent single sensor failure.

Environmental over temperature protection: When the internal temperature of the controller exceeds 85 ° C, the protection is triggered to avoid self failure.

Reset method:

LF/LV: Supports panel RESET button reset or external momentary normally open switch reset (terminal 9), reset requires temperature to drop below "set point hysteresis".

LS: Only supports power-off reset (power must be disconnected for ≥ 3 seconds) to prevent accidental operation and release protection, in compliance with safety level design.

Core functions and operation guide

1. Core functional features

(1) Independent security logic

It has no electrical connection with the main controller, independent power supply, independent sampling, and independent output. Even if the main controller loses control (such as output adhesion), it can still monitor the temperature and cut off the load through its own sensors, avoiding "common cause faults".