DS3800XTFT1B1A | Replace DS3800XTFT GE I/O

Description

Product Introduction

The DS3800XTFT1B1A is a specialized variant of GE’s differential frequency board—factory-configured for 24V logic-level signals with fixed trigger thresholds, but retaining the differential inputs and 50 kHz range of the full XTFT series. The “B” in the suffix tells you the input logic is set for 24V DC (rather than the wide 0.5-24V programmable range), and the “A” at the end indicates acrylic conformal coating.

This board is the sweet spot for plants running 24V sensors in noisy environments. It gives you the noise rejection of differential inputs—up to 100dB CMRR at 60Hz—without the complexity of per-channel threshold programming. The fixed 12V trigger with 4V hysteresis is ideal for 24V proximity sensors, encoders, and pulse generators, and the wide 50 kHz range covers everything from low-speed shaft encoders to high-frequency flow meters. The conformal coating adds protection against humidity and dust, making it suitable for non-climate-controlled cabinets. Typical buyers are plant engineers with 24V-only sensor networks who need the best noise rejection available in a Mark VIe frequency board.

Key Technical Specifications

Compatible Replacement Models

Frequently Asked Questions (FAQ)

Q: Can I hot-swap this board?

No. The Mark VIe backplane does not support live insertion. Power down the entire I/O pack before removal. The differential front-end is sensitive—hot-swap attempts can damage the input protection circuitry.

Q: What does the “B” configuration mean?

The “B” in DS3800XTFT1B1A indicates a factory-fixed 24V logic input. The trigger threshold is set to 12V ±1V with 4V hysteresis. This is ideal for:

• 24V proximity sensors (PNP output, 24V logic level)
• 24V pulse generators (square wave, 24V amplitude)
• 24V encoder outputs (push-pull or open-collector with pull-up)

It is not suitable for 5V logic (TTL) or low-level magnetic pickup signals. If you have those, use the programmable XTFT.

Q: How is the 1B1A different from the standard XTFT?

Two main differences:

• Fixed vs. programmable thresholds: The standard XTFT has programmable thresholds per channel (0.5V to 24V). The 1B1A has fixed thresholds set at 12V for all channels.
• Coating: The “A” suffix indicates acrylic coating. The base XTFT has no coating.
• Input impedance: The 1B1A uses 4.7kΩ input impedance (optimized for 24V logic), while the standard XTFT uses 10kΩ.

The differential inputs, 50 kHz range, 32-bit counters, and CMRR specs are identical.

Q: How does the differential input help with 24V signals?

With single-ended inputs (like the XTFS), noise on the cable ground can cause false triggering. With differential inputs, the board measures the voltage difference between the two wires. Common-mode noise (like 60Hz hum from nearby power cables) appears equally on both wires and is rejected—you get clean triggering even on long cable runs.

In practical terms: you can run twisted-pair cable up to 300 meters with this board, compared to about 50 meters with a single-ended board.

Q: How do you test this board before shipping?

We run an 8-step test with a precision differential pulse generator up to 50 kHz:

• Visual inspection: Check for cracked connectors, burnt traces, swollen capacitors. Inspect the coating for uniformity.
• ESD check: Insulation resistance between channels and chassis ground >10MΩ.
• Power-up: Apply +5V DC, measure current draw (1.6A ±10%).
• Communication handshake: Simulate backplane connection, verify board ID.
• Common-mode rejection test: Inject a 1 kHz, 1V differential signal while applying a 10V, 60Hz common-mode voltage. Verify the board measures the differential signal with <0.1% error.
• Trigger threshold verification: For each channel, inject a 1 kHz differential pulse and sweep the input voltage from 0V to 30V. Verify triggers at 12V ±1V with 4V hysteresis.
• Frequency accuracy test: Inject known frequencies (1 Hz, 100 Hz, 1 kHz, 10 kHz, 20 kHz, 50 kHz) and verify accuracy within ±0.05%.
• 24-hour soak: Run at 50°C ambient with all channels at 10 kHz. Log frequency readings every hour—failure threshold is ±0.1% deviation.

We reject about 4% of these boards—the fixed-threshold comparators are simpler, so failure rates are slightly lower than the programmable version, but the differential front-end adds complexity.

Q: What’s the most common failure on this board?

Three things specific to the differential fixed-logic design:

• Input resistor matching drift: The differential amplifier relies on matched resistor pairs. Over time, resistor drift can degrade common-mode rejection. We replace the input resistor network on about 10% of refurbished units.
• Optocoupler degradation: The differential optocouplers degrade with age, especially if subjected to over-voltage. We replace them on about 15% of refurbished units.
• Coating-related heat: The acrylic coating traps a little heat—about 1-2°C at the differential amplifier. The board’s calibration accounts for this, but if your cabinet exceeds 55°C, the CMRR can degrade.

Q: What input signals can I use with this board?

24V logic signals only, with differential output. Acceptable sources:

• PNP proximity sensors (24V output) with differential output
• 24V pulse generators (square wave)
• 24V open-collector outputs with pull-up resistors
• Differential encoder outputs (A+/A- type)

Do not connect:

• 5V TTL signals (won’t trigger)
• Magnetic pickups (voltage is too low and AC)
• 48V or higher signals (will damage input circuits)
• Single-ended sensors (you need both wires for differential)

Q: What cable should I use?

Twisted-pair shielded cable. Connect:

• Signal+ to the positive input
• Signal- to the negative input
• Shield to ground at the rack side only

For cable runs over 100 meters, use 22 AWG or thicker to minimize voltage drop. The differential input rejects common-mode noise, so shielding is less critical than on single-ended systems, but we still recommend it for long runs.

Q: Can I use this board for primary overspeed protection?

No. The minimum gate time is 50ms—too slow for primary overspeed (requires <20ms response with hardware interlock). Use this for speed monitoring, trend analysis, and backup alarms. Keep the dedicated overspeed trip system.

Q: Are there counterfeit versions of this board?

Yes. Look for:

• Input resistor networks: Genuine boards use precision matched resistor arrays (0.05% tolerance). Counterfeits use discrete resistors with 1% tolerance—CMRR will be degraded.
• Differential amplifier IC: Genuine boards use a high-performance instrumentation amplifier. Counterfeits use generic op-amps with lower CMRR.
• Optocouplers: Genuine high-speed optocouplers. Counterfeits use slower optocouplers that can’t handle 50 kHz.
• Coating: Genuine coating is uniform and matte. Fakes use cheaper lacquer.
• Label: Genuine—matte finish, greenish barcode. Fakes—glossy.

We trace stock to decommissioned assets. If buying elsewhere, demand photos of the component side and serial sticker, especially close-ups of the input resistor networks and amplifier IC.

Q: What’s your warranty?

1-year against functional defects. For differential boards, we guarantee the CMRR performance for the warranty period—if it degrades out of spec, we’ll recalibrate or replace it.

Q: What’s the lead time?

We typically carry 2-3 units. Orders before 2 PM EST ship within 1-2 business days after testing. The 24-hour soak is mandatory—we won’t skip it. Expedited shipping available with waiver. For critical speed monitoring applications, we recommend waiting for the full test cycle—the differential amplifier and resistor matching only show CMRR degradation after hours of thermal stress.

ABB 3HAC025338-006
GE WESDAC D20A/0511-01010
B&R 4PP220.0571-45
HONEYWELL CC-PDIL51