DS4815OIFA | GE Surplus – Ready to Ship

Description

Product Introduction

Not every application needs separate input and output boards. The DS4815OIFA packs eight 4-20mA inputs and eight 4-20mA outputs into a single Mark V slot—perfect for smaller turbine installations or retrofit projects where rack space is at a premium. It handles the standard process signals: pressure transmitters, temperature transmitters (with external transmitters), and actuator positioners.

Compared to the DS4815OIF (non-A revision), the “A” revision brings a handful of incremental improvements: the output loop power supply was upgraded from 18V to 22V, giving you more headroom for driving long cable runs. The input burden resistor tolerance improved from 0.5% to 0.1%, boosting overall system accuracy. The terminal assignment is identical—just drop it in. No firmware changes required.

Key Technical Specifications

Compatible Replacement Models

Frequently Asked Questions (FAQ)

Q: What’s the main advantage of the OIFA over the OIF?
The output compliance voltage—22V vs. 18V. A 4-20mA loop needs enough voltage to push 20mA through the load and the wiring. With a 250Ω load and 100 feet of 18 AWG wire, you need about 5.5V at the load. At 18V compliance, you’re left with 12.5V margin—enough for most applications. At 22V, you get 16.5V margin, which allows for longer cable runs (up to 1000 feet with 18 AWG). The A revision also improves the burden resistor tolerance, which is critical for high-accuracy measurements.

Q: How do I wire a 2-wire 4-20mA transmitter to the OIFA?
A 2-wire loop-powered transmitter needs power from the loop. The OIFA’s outputs can provide that power—connect the transmitter as follows: Output+ (OFA terminal) to Transmitter+, Transmitter- to Input+ (IFA terminal), Input- back to Output- (0V). The output provides the 24V loop power; the input reads the current. This is the most common field wiring configuration. If you’re using a 4-wire transmitter with separate power, you don’t need the output power—connect Transmitter+ to 24V field supply, and the signal leads to Input+ and Input-.

Q: The input is showing 4mA when it should be 12mA. What’s causing this?
You may have an open-loop condition. The OIFA detects open loops by measuring the current—if it’s below 2mA, it flags an open. A reading of exactly 4mA could mean the transmitter is at zero scale (which is correct) or the loop is broken but the board’s internal pull-down keeps it at 4mA (unlikely). Check the transmitter’s configuration—is it set to 0-20mA instead of 4-20mA? If so, the zero offset is wrong. Also check the wiring: a loose connection on the Input- terminal can cause intermittent readings.

Q: The output is not driving the full 20mA. What’s the max load resistance?
At 22V compliance, the maximum load is 22V / 20mA = 1100Ω. That includes the wiring resistance and the load. For example, a 500Ω actuator valve uses 10V of the compliance, leaving 12V for the wiring. With 18 AWG wire (0.006Ω/ft), you can run up to 1000 feet (round trip) before the voltage drop exceeds 12V. If your load is 750Ω, the max cable length drops to about 500 feet. The older OIF had an 18V compliance—max load 900Ω—so the OIFA gives you a 22% increase in load capacity.

Q: The fault LED is red, but both inputs and outputs seem to be working. What does that mean?
A red fault LED on the OIFA typically indicates an internal overtemperature condition (above 80°C on the board’s heatsink). The board will continue to operate, but accuracy may degrade. If the temp reaches 85°C, the board will start folding back the output current. Check the cabinet’s airflow—the OIFA runs hotter than a pure input or output board because it has both analog and output circuitry. If the cabinet is above 50°C ambient, you may need to derate the outputs. We’ve seen this on plants with poor airflow.

Q: Can I use the OIFA’s outputs for 4-20mA valve positioners?
Yes, that’s a common application. The outputs have enough compliance (22V) to drive most valve positioners (which typically have a 250-500Ω input impedance). Just ensure the total loop resistance (positioner + cable) doesn’t exceed 1100Ω. The OIFA’s outputs are short-circuit protected, so you won’t damage the board if the positioner is miswired.

Q: The input readings are noisy. What’s the most likely cause?
Ground loops. The OIFA has differential inputs, but if the transmitter and the board have different earth potentials, you’ll see noise. Measure the AC voltage between the transmitter’s 0V and the rack’s 0V—if it’s above 0.5V AC, you have a ground loop. Use a signal isolator or ensure both share the same earth ground. Also check the input wiring—unshielded cables running near VFDs will pick up noise. Use shielded twisted pair and ground the shield at the rack end only.

Q: Does the OIFA support 0-10V inputs or outputs?
The standard OIFA is 4-20mA only. However, there are variants with the “B” suffix that support 0-10V outputs, and some with “C” for HART pass-through. Check your board’s part number carefully—if you have a standard OIFA, you’ll need external signal conditioners to convert 0-10V to 4-20mA. If you have the B variant, confirm the voltage range with the pinout diagram.

Q: What’s the input sample rate and how does it affect the control loop?
The OIFA samples all 8 input channels at 50 Hz (20ms per sample). That’s fast enough for most turbine control loops (speed, temperature, pressure). If you have a high-speed application (e.g., vibration or fast pressure transients), you’ll need a dedicated high-speed input board (e.g., DS4815HSIA). The OIFA’s sample rate is fixed—you can’t increase it.

Q: What’s the lead time for a surplus OIFA?
We keep 4-6 units in stock. Domestic: 2-3 business days ground, overnight if ordered by 2 PM EST. International: 5-7 days via DHL, with customs potentially adding 1-3 days. This board is not ITAR-controlled, so we can ship to most countries without an export license. We include a GE certificate of origin and commercial invoice with every shipment. If you need the board urgently for a critical outage, we can arrange expedited shipping—contact us for options.

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