Description

Key Technical Specifications

Parameter	Value
Measured Quantity	Sinusoidal AC current (single-phase)
Accuracy Class	0.5%
Auxiliary Supply	24 VDC; 48–110 VDC; 88–220 VDC; 110/230 VAC; 440 VAC
Output Signal	DC current or DC voltage, proportional to measured value
Output Slope Configuration	Up to 3 configurable slopes
Configuration Method	Factory pre-configuration or PC-based configuration tool
Input / Output Connection	Screw terminal blocks
Measurement Circuit Voltage	Up to 690 V
Housing / Mounting	Compact DIN-rail or panel-mount unit
Typical Downstream Devices	PLC, PC, microprocessor control, indicators, alarm units
Product Status	Phased out by OEM (no listed direct successor)

Product Introduction

A dead 4-20mA loop will shut down a boiler feed pump faster than any alarm. I’ve traced too many of those to a failed transducer nobody knew existed until the signal dropped. The DEIF TAC-311DG is the unit that sits in that gap — a single-function AC current transducer from DEIF’s TAC-300 range, built to measure sinusoidal AC current on a single-phase network and hand a proportional DC current or voltage signal to the PLC, the DCS historian, or a local alarm module. You’ll find these bolted inside generator control panels, switchgear cubicles, and skid-mounted power packages from shipyards to mining substations.Engineers pick it for one reason: it does exactly one job and does it predictably. Accuracy sits at 0.5%, the auxiliary supply accepts 24 VDC through 220 VDC and 110/230 VAC or 440 VAC, and up to three output slopes can be configured — either pre-set at the factory or dialed in with DEIF’s PC tool. That multi-slope capability is the quiet feature that saves you a second transmitter when a pump needs both a run-current window and an overload window. Subjective note: this revision is picky about auxiliary supply polarity and grounding — get it wrong and you’ll chase a phantom 2mA offset for a week. Get it right, and it runs for a decade.

Quality SOP & Tech Pitfalls

The Lab Report (SOP)Every unit that leaves our shelf goes through the same five steps, in this order:

Visual / counterfeit check — housing mold lines, terminal block finish, laser-etched model suffix, DEIF label font. Fakes in this price bracket are common.
Live test on the test rack — 24 VDC auxiliary applied, known AC current injected via a calibrated source, output read on a Fluke 115 and a 6½-digit DMM.
Insulation resistance and continuity checks — 500 V megger between aux supply and signal loops; terminal-to-terminal continuity against the wiring diagram.
Firmware / configuration version logging — the configured slope set and any PC-tool parameters are recorded and photographed.
Anti-static sealing — ESD bag, desiccant, sealed label with test date and technician ID.

The Engineer’s Warning (Pitfalls)Two mistakes cause most of the downtime I’ve seen with this model.First: configuration mismatch. The TAC-311DG can be factory pre-configured or configured by PC tool. A “new” unit with default slopes dropped into a panel expecting a 2-slope profile will read plausible numbers — just wrong ones. Your PLC won’t fault. Your process will drift. I once spent a Saturday on a mine dewatering skid because a replacement arrived with factory defaults while the old unit had a custom 4-20mA slope set for a 0–250A CT ratio. The current looked fine. The pump trip point was 40A off.Second: photograph before you pull. Old DIP/jumper settings, CT ratio links, and terminal polarity must be documented before removal. This model has no display to confirm what it was set to. No photo, no recovery.

Installation & Configuration Guide

Phase 1 — Pre-Installation

️ De-energize the circuit. Isolate the AC current circuit and the auxiliary supply. Lock out, tag out, verify dead with a rated voltage tester.
️ Wait for discharge. Allow capacitors in adjacent panels to bleed — give it five minutes minimum.
️ Photograph everything. Old wiring, terminal labels, DIP/jumper positions, CT polarity marks, and the nameplate of the outgoing unit.

Phase 2 — Removal

Label each wire with its terminal number before loosening anything.
Release the DIN-clip retaining tabs with a flat screwdriver — pry evenly, don’t torque one side.
Pull the module straight off the rail. Inspect the rail and adjacent units for heat discoloration.

Phase 3 — Installation

Copy the DIP/jumper and CT ratio settings from your photos onto the new unit before it touches the rail. This single step prevents roughly 90% of startup failures on this model.
Seat the module fully on the DIN rail until the clip engages with an audible click.
Torque terminals to the OEM specification — under-torque drifts, over-torque cracks the block.

Phase 4 — Power-On & Testing

Confirm 24 VDC (or the configured aux voltage) at the supply terminals with a multimeter before energizing the AC circuit.
Observe the LED boot sequence; compare against the installation manual.
Inject a known current or use a clamp meter to verify output against the PLC reading at three points: low, mid, high.
Download and verify the configuration file; archive the final parameter set in your maintenance records.

Compatible Replacement Models

Option	Tier	Notes
DEIF TAC-321DG	️ Software / Configuration Compatible	Same single-function current measurement family, but requires no auxiliary supply — wiring changes at the aux terminals are unavoidable, and the configuration must be rebuilt. Budget 2–4 hours plus commissioning.
DEIF TAS-311DG / TAS-321DG / TAS-331DG	️ Migration Path	Current DEIF standalone transducer line with published configuration manuals and installation instructions. Requires new configuration and terminal re-verification.
DEIF TAV-311DG / TAV-321DG	Not Applicable	These measure voltage, not current. Do not substitute.
Third-party 4-20mA current transducers	Hardware Mod Required	Different mounting, burden, and aux supply. Only consider as part of a full panel upgrade.

Frequently Asked Questions (FAQ)

Can I hot-swap this safely?
No. This isn’t a hot-swappable I/O card. The AC current circuit and the auxiliary supply must both be isolated. Pulling a live CT secondary can produce a dangerous high voltage — kill the primary circuit first.Is the TAC-311DG still available new?
Not from the OEM. DEIF has phased it out and lists no direct replacement. What you’ll find in the channel is new surplus and factory-sealed old stock. Ask your supplier for the manufacture date and test record before buying.Will a TAC-321DG drop straight in?
Functionally close, physically not identical. The -321DG needs no auxiliary supply, so your aux wiring becomes dead ends and the configuration has to be rebuilt. Plan for a few hours of labor, not a five-minute swap.Why does my new unit read a constant offset?
Nine times out of ten: wrong CT ratio setting, reversed polarity, or a missing ground reference. Check the DIP/jumper copy against your photos first, then the polarity marks. Only after that should you suspect the module.Do I need the DEIF PC tool to configure it?
You need it if you’re changing slopes or ranges. If your supplier ships a factory pre-configured unit matching your old settings, you can skip the tool — but verify the output at three points anyway.What warranty should I expect on obsolete stock?
Reputable suppliers typically offer a one-year warranty and a short acceptance window on this model. Get it in writing. For a discontinued part, that paper matters more than the discount.Can I parallel two TAC-311DG units on one CT?
Not without checking the CT burden rating. Two transducers on one secondary double the burden and can push the CT out of its accuracy class. Measure the total burden against the CT datasheet first.