2MLF-AV8A Honeywell ML200 Analog Voltage Input Board

Description

Product Model: 2MLF-AV8A
Product Brand: Honeywell
Product Series: MasterLogic-200 / Analog I/O Modules

Key Features:

• 8 independent voltage input channels supporting multiple ranges (e.g. 1-5 V, 0-10 V, –10-10 V, etc.)16-bit data format (14-bit precision), conversion speed ~ 250 µs per channel
• High input resistance (≥ 1 MΩ) — minimal loading on source
• Photo-coupler isolation between each input terminal and PLC power rail (no per-channel isolation)

Product Role & System Fit

In Honeywell’s MasterLogic-200 (ML200) PLC architecture, analog modules like 2MLF-AV8A provide the interface between external voltage signals (e.g. from sensors, transducers, signal conditioners) and the PLC’s internal digital logic. While digital I/O handles discrete signals (on/off), analog I/O modules convert continuous measurements into values that can be used by control logic, trending, or diagnostics.

The 2MLF-AV8A is specifically a voltage input module (i.e. it expects voltage signals, not current) with eight independent channels. Its counterpart in the ML200 line is 2MLF-AC8A, which handles current input types.

Within a PLC rack, 2MLF-AV8A plugs into the analog I/O section. Each channel’s analog input is sampled, digitized, filtered or averaged (depending on configuration), and the resulting value is made available via internal registers to the CPU or control program. Because its input resistance is very high (≥ 1 MΩ), sources see minimal loading from this module.

Designers choose it when your system must measure multiple voltage signals (e.g. 0–5 V, 0–10 V, –10–10 V) and feed those into the logic layer for comparisons, control decisions, alarms or logging.

Technical Features & Benefits

Let’s break down what the 2MLF-AV8A offers in real-world settings, and where its design strengths or caveats lie.

Analog Ranges & Data Format

The module supports several analog input ranges, including:

• DC 1–5 V
• DC 0–5 V
• DC 0–10 V
• DC –10 to +10 V
  These configurable ranges let you match many common sensors or signal conditioners.

The module produces a 16-bit digital output, with 14-bit precision (i.e. internal resolution supporting fine gradations). Digital output formats can be configured per channel: unsigned, signed, “precise” value, or percentile format.

The conversion speed is ≈ 250 µs per channel, meaning that for 8 channels the total scanning time is manageable.

Input Resistance & Isolation

For voltage inputs, input resistance is ≥ 1 MΩ (minimum). That ensures the module loads very little on sensors or signal sources, which is especially important when dealing with weak signals or long wiring runs.

Between the input terminals and the PLC’s power/logic side, the module uses photo-coupler isolation. However, it does not provide isolation between individual channels. That means channel-to-channel isolation is not guaranteed; all inputs share a common reference.

Precision, Accuracy & Drift

At ambient 25 °C (±5 °C), the accuracy is about ±0.2% for a given input range, and across full range (0 to 55 °C), ±0.3%.

Offset and gain values are factory-tuned and cannot be modified by users.

Because of those limitations, for high-precision or calibration-critical loops, you must choose ranges carefully and compensate for wiring losses if needed.

Internal Consumption & Module Details

The module draws DC 5 V: 420 mA internally from the PLC’s 5 V bus.

The module is relatively lightweight — about 140 grams.

It terminates via an 18-point terminal block connector (M3 screw) for field wiring.

A RUN LED on the module indicates normal operation; flickering means error (e.g. parameter mismatch or conversion fault), and off means power missing or module failure.

Signal Filtering, Averaging & Error Detection

The 2MLF-AV8A supports:

• Filter processing per channel (enable/disable), with filter constants adjustable
• Average processing (count average or time average) to smooth out noise
• Special monitoring / test modes, where you can observe min/max, reset them, or temporarily override parameters during debugging

It also includes built-in diagnostics: offset/gain errors, wiring errors, status flags, error codes for channels.

When an analog input value goes beyond the configured range, the digital output saturates at the maximum or minimum value (clamping) rather than rolling over.

All these features allow the programmer or maintenance staff to detect sensor faults, drift, or wiring issues before control performance degrades.

Technical Specifications Table

Installation & Maintenance Insights

Here are practical tips drawn from field practice and the module’s user guide:

Wiring & Layout

• Use twisted shielded pair cable for each analog input to reduce noise. The module manual recommends AWG 22 (0.3 mm²) cable or bigger.
• Maintain physical separation from AC wiring or power lines to avoid inductive pickup.
• Avoid long wiring runs if possible; voltage drop or line resistance can introduce measurement error, especially in ranges near full scale. The user guide includes formulae relating cable resistance, source resistance, and error tolerance.
• Check wire polarity carefully: since this is voltage input, errors in polarity can lead to erroneous or out-of-range readings.

Module Setup & Configuration

• After installation, configure ranges (per channel) via SoftMaster (or equivalent parameter tool) for desired ranges (e.g. 1–5 V, 0–10 V).
• Enable or disable filter/average processing per channel depending on noise environment.
• Use special module monitoring to read min/max, test live values, or debug channel conversions.
• Always disable unused channels to free scanning time and reduce conversion load.

Troubleshooting

• If the module’s RUN LED flickers, consult error codes for offset/gain mismatches or wiring faults.
• If digital values are pegged (max or min), check if the analog input is out of configured range or wiring is broken.
• Re-check cable termination and shielding if random noise or drift appears.

Maintenance

• Periodically inspect terminal tightness; vibration over time can loosen screws.
• Check connector integrity and look for corrosion or residue.
• Validate calibration drift by injecting known voltage values (e.g. 1 V, 5 V, 10 V) and comparing digital conversions.
• Keep firmware / module model records; replacement modules must match the same model (2MLF-AV8A) or behavior differences occur.

Because analog modules often live in difficult environments, regular checks help prevent subtle drift or signal degradation over time.

Related Modules

Here are some analog and I/O modules in the same ML200 family for comparison:

• 2MLF-AC8A — 8-channel current input module (4–20 mA etc.) (counterpart)
• 2MLF-AD8A — Differential analog input version in the same series
• 2MLF-DV8A — Analog output module 8 channels (voltage)
• Other ML200 I/O modules (digital input/output, special modules) — used when combining analog and discrete I/O in a system

These sibling modules share mechanical form factors, communication methods, and backplane support, making them easier to mix in a system.