UT-150L

The Yokogawa UT150L is a digital limit controller designed to monitor process variables and provide high-limit or low-limit protection based on a configured setpoint. It features a universal measurement input, latching limit action, two optional alarm outputs, and a maximum-value register. The 1/16 DIN panel-mounted instrument also supports optional RS-485 communication and PV retransmission, depending on the ordered configuration.

Limit Control Function

The UT150L monitors a measured process variable (PV) against a configured limit setpoint. It can operate as either a high-limit or low-limit controller, allowing the trip direction to match the monitored process condition.

Its latching limit action retains the limit event until the appropriate reset operation is performed. This behavior distinguishes limit protection from ordinary continuous PID temperature regulation.

The controller also provides a timer for recording the duration that the setpoint is exceeded and a register for retaining the maximum temperature reached.

Universal Measurement Input

The universal input supports different sensor and signal types selected through software configuration. Supported input categories include thermocouples, resistance temperature detectors (RTDs), and DC voltage signals.

The selected input type and range must correspond to the connected sensor or transmitter. Input configuration therefore needs to be checked when replacing an existing controller, particularly when the replacement uses a different sensor type or measurement range.

Control Output and Limit Relay Operation

The UT150L uses a single relay contact as its limit control output. When the measured value exceeds the configured setpoint, the relay de-energizes and the OUT indicator remains active even after the process value returns to its normal range.

The output remains in the de-energized state until an operator performs the confirmation operation. Confirmation is not accepted while the measured value continues to exceed the setpoint. This latching behavior allows the limit event to remain visible for operator attention.

Alarm and Retransmission Options

The controller supports additional functions through selectable option codes:

• /AL: Two alarm relay outputs with 22 selectable alarm types, including PV high/low limits, deviation alarms, fault diagnosis and FAIL output.
• /RET: 4-20 mA DC retransmission of the measured process value, with a maximum load resistance of 600 ohms.
• /EX: One external contact input for resetting the exceeded status.
• /RS: RS-485 communication interface supporting PC link, ladder communication and MODBUS protocols.

The /RS and /EX options cannot be specified simultaneously. These options must be verified against the complete instrument ordering code rather than assumed to be included in every UT150L unit.

Technical Specifications

Parameter	Specification
Model	UT150L
Brand	Yokogawa
Product Type	Digital Limit Controller
Controller Size	1/16 DIN
Measurement Input	1 universal input
Input Types	Thermocouple, RTD, DC mV and DC V
Input Configuration	Software selectable
Input Sampling Period	500 ms
Thermocouple Input Accuracy	+/-2 deg C +/-1 digit, subject to sensor-specific conditions
RTD Input Accuracy	+/-1 deg C +/-1 digit
Voltage Input Accuracy	+/-0.3% +/-1 digit
Limit Control	High-limit or low-limit operation
Limit Action	Latching output
Control Output	1 relay contact
Relay Contact Capacity	3 A at 240 VAC or 3 A at 30 VDC, resistive load
Alarm Outputs	2 relay contacts with /AL option
Alarm Relay Capacity	1 A at 240 VAC or 1 A at 30 VDC, resistive load
Retransmission Output	4-20 mA DC with /RET option
Contact Input	1 point with /EX option
Communication Interface	RS-485 with /RS option
Communication Protocols	PC Link, Ladder Communication, MODBUS
Maximum Communication Distance	1,200 m
Maximum Connected Controllers	31
Power Supply	100-240 VAC +/-10%, 50/60 Hz
Maximum Power Consumption	8 VA
Front Panel Protection	IP65
Mounting	Flush panel mounting
Terminal Type	Screw terminals
Panel Cutout	45 x 45 mm (+0.6/0)
External Dimensions	48 x 48 mm front panel
Ambient Operating Temperature	0 to 50 deg C; 0 to 40 deg C for side-by-side mounting
Ambient Humidity	20-90% RH, non-condensing
Warm-up Time	At least 30 minutes
Storage Temperature	-25 to 70 deg C
Safety Approval	FM-3810 and FM-3545
Safety Standards	IEC/EN 61010-1, UL508, CSA C22.2 No. 61010-1

Specifications based on Yokogawa General Specifications GS 05C01E22-01E. Option-dependent functions require the corresponding ordered configuration.

Installation and Configuration Considerations

The UT150L is designed for flush panel mounting with screw-terminal connections. Its front panel provides IP65 dust-proof and drip-proof protection under the specified mounting conditions. This protection is not maintained when multiple controllers are installed side by side.

For replacement applications, verify the panel cutout, supply voltage, sensor input configuration, relay contact requirements and installed option codes. The controller requires a minimum 30-minute warm-up period under the manufacturer's specified operating conditions.

Frequently Asked Questions

Q: Can the Yokogawa UT150L operate as both a high-limit and low-limit controller?

A: It can be configured for either high-limit or low-limit operation. The selected limit direction determines whether the controller responds when the measured process value rises above or falls below the configured threshold.

Q: Does every UT150L include RS-485 communication and two alarm outputs?

A: No. RS-485 communication requires the /RS option, while two additional alarm relay outputs require /AL. The /RS and /EX options are mutually exclusive and cannot be specified together.

Q: Can the UT150L retransmit its measured temperature to another controller or monitoring system?

A: Yes, when equipped with the /RET option. It provides a 4-20 mA DC retransmission signal representing the measured process value, with a maximum load resistance of 600 ohms.

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