1746sc-CTR8 is an 8-channel high‑speed counter and flowmeter input module by Spectrum Controls, built for the Allen‑Bradley SLC 500 chassis platform. It is the higher‑density sibling of the 1746sc-CTR4, designed for systems requiring many simultaneous pulse inputs from flow transmitters, encoders, speed pickups and batch metering devices. The module accepts both DC logic pulses and low‑level AC variable reluctance signals directly from turbine flow meters, removing the requirement for external signal conditioning in most custody transfer and process metering installations.

Its flexible channel architecture allows configuration either as eight independent single‑ended pulse counters, or grouped into four quadrature encoder pairs for position and direction tracking. Each channel supports dedicated enable and reset logic, programmable K‑factor scaling, filtering, preset values and rate calculation. Field inputs are optically isolated from the SLC backplane to protect the PLC from electrical transients and ground loops common in refineries, pipelines and chemical plants. The module integrates natively with RSLogix 500 and works with SLC 5/03, 5/04 and 5/05 processors. It is end‑of‑life and no longer produced, making verified tested stock essential for legacy flow and motion control systems.

We supply visually inspected and functionally validated 1746sc-CTR8 units, including new old stock and refurbished surplus inventory. Every module is checked for backplane communication, full‑range pulse capture, quadrature response, scaling calculation and terminal integrity before shipment, ready for direct drop‑in installation into existing SLC 500 racks.

Key Features

Spectrum Controls 1746sc-CTR8, 8-channel counter and flowmeter input module for SLC 500 Max input frequency up to 50 kHz for both DC and AC variable reluctance signals Configurable channel layout: 8 single counters or 4 quadrature encoder pairs Supports 5 VDC, 12 VDC, 24 VDC pulse inputs and VR flowmeter signals from 50 mV peak up to 75 V peak Four external enable/reset control lines for batch totalising and meter proving Programmable K-factor, scaling, preset limits and selectable digital / hardware filtering Optical isolation between field inputs and SLC backplane (1000 VDC isolation rating) Two selectable count ranges: ±32,767 and ±8,388,607 Fixed 4 ms per-channel update cycle, decoupled from PLC scan time Removable screw terminal block for easier wiring and module exchange Compatible with SLC 5/03, SLC 5/04 and SLC 5/05 processors Software configuration via RSLogix 500 data table mapping ISA‑S71.04 G3 industrial contaminant rating EOL legacy specialty I/O, available only as tested surplus and NOS spare

Product Specifications

Part number: 1746sc-CTR8 Manufacturer: Spectrum Controls, compatible with Allen‑Bradley SLC 500 Platform: SLC 500 PLC Module type: High‑speed counter / flowmeter input Channel count: 8 independent channels, configurable as 4 quadrature pairs Max frequency: 50 kHz, AC and DC inputs DC input levels: 5 VDC, 12 VDC, 24 VDC AC VR flowmeter input: 50 mV to 75 V peak Count ranges: ±32,767; ±8,388,607 Isolation: 1000 VDC, field to backplane Backplane power draw: 225 mA @ 5 VDC; 125 mA @ 24 VDC Max power dissipation: 1.75 W Update time: 4 ms per channel Operating temperature: 0 °C to +60 °C Humidity: 5%–95%, non‑condensing Input impedance: 25 kΩ Mounting: Single slot in standard SLC 500 I/O chassis Software: RSLogix 500 Lifecycle status: End-of-life, discontinued production

Typical Applications

Multi-stream gas and liquid turbine flow metering Chemical blending, batch filling and custody transfer skids Packaging machinery multi‑axis encoder position tracking Conveyor speed monitoring and part counting Refinery and pipeline flow totalisation Water and wastewater pulse flow measurement Food & beverage ingredient dosing and batch control Rotating machinery speed pickup and overspeed monitoring SLC 500 system spare stocking and plant outage maintenance Retrofit of multi‑channel pulse measurement panels

Why Choose Our 1746sc-CTR8 Module

We specialise in hard-to-source Spectrum Controls and Allen‑Bradley discontinued SLC 500 specialty I/O for plant maintenance teams, system integrators and automation contractors. Because flow custody transfer and encoder position loops cannot tolerate missed pulses, each 1746sc-CTR8 undergoes full frequency response, quadrature and scaling testing, alongside backplane communication validation before dispatch.

We consolidate shipments with other SLC spares, including 1746sc-CTR4, 1746-P3, 1746-OA16 and 1746-NR8. Formal commercial invoices, packing lists and optional test records are available on request. Tiered pricing and long‑term plant spare frame agreements are supported for bulk procurement. Submit your full part list and target delivery time for a custom quotation.

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FAQ

What is the main difference between 1746sc-CTR8 and 1746sc-CTR4? The CTR4 has four channels, while CTR8 provides eight channels and supports up to four quadrature encoder pairs instead of two. They share the same 50 kHz maximum frequency and VR flowmeter capability, but they are not pin‑compatible and use different terminal assignments.

Can it read variable reluctance turbine flowmeters directly? Yes, it accepts low‑level AC VR signals without an external preamplifier, one of its core advantages for multi‑stream metering skids.

Can I mix quadrature channels and simple pulse counters on the same module? Yes. You can assign some channels for single pulse counting and group others into quadrature A/B/Z encoder pairs according to your wiring and RSLogix 500 configuration.

Is it compatible with SLC 5/01 and 5/02? Officially targeted for SLC 5/03, 5/04 and 5/05. Older SLC 5/01 and 5/02 processors lack sufficient interrupt and backplane bandwidth and are not recommended.

Is the 1746sc-CTR8 still in production? No, Spectrum Controls has discontinued this model. New factory stock is unavailable; supply is limited to new old stock and functionally tested surplus units.

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1746SC-CTR4