Key Technical Specifications
- Product Model: SG-004A
- Manufacturer: FNIRSI
- Primary Function: Signal Generation & Simulation
- Output Signals: 4-20mA, 0-10V, Thermocouple (J/K/T/E/N/R/S/B), RTD (PT100/CU50)
- Loop Power: Built-in 24V DC Power Supply
- Display: LCD with Backlight
- Accuracy: ±0.05% F.S. (Typical)
- Power Source: Rechargeable Lithium Battery
- Portability: Handheld Pocket Size
- Application: Field Instrumentation & PLC I/O Testing
Product Introduction
You’re standing in front of a control panel, and the HMI says the tank is empty, but your gut says it’s full. You can’t trust the process variable until you’ve forced a known signal into the system. The FNIRSI SG-004A is that trust builder. It’s a compact, battery-powered workhorse designed to inject precise 4-20mA signals or simulate temperature sensors right at the field device or PLC input card.I keep one of these in my tool bag because it solves the “is it the sensor or the wire?” debate in about thirty seconds. The core value here is the built-in 24V loop power; you don’t need to hunt for a separate power supply to test a two-wire transmitter. It’s not a Fluke 754, and it doesn’t cost a grand, but for quick loop checks and verifying RTD inputs, it gets the job done without making you cry over the price tag. Just keep it away from high-voltage panels, as the input protection on these budget calibrators isn’t bulletproof.
Quality SOP & Tech Pitfalls
We don’t sell blind. Every SG-004A gets a sanity check before it ships. First, we do a visual inspection to ensure the BNC/terminal connectors aren’t cracked from previous abuse. Then, we hook it up to a precision multimeter and verify that when it says it’s outputting 12.00mA, it’s actually pushing 12.00mA, not 11.8mA. We check the 24V loop supply under load to make sure it doesn’t sag, and we verify the battery charges correctly. Finally, it gets packed in anti-static foam.Here is the trap that catches everyone: Don’t mix up “Source” and “Simulate.” I’ve seen techs spend an hour troubleshooting a PLC input because they had the calibrator in “Source” mode (which outputs voltage) instead of “Simulate” mode (which acts like a passive transmitter). Also, watch your polarity. These units aren’t as forgiving as the big yellow Flukes. Reverse the leads on a live 24V loop, and you might let the magic smoke out. Treat it like a precision instrument, not a hammer.
Installation & Configuration Guide
- Pre-Check Safety: ⚠️ Verify the loop is de-energized if you are breaking the circuit. If you are just simulating a sensor at a PLC input, ensure the channel is configured for the correct sensor type in the software first. Take a photo of the wiring before disconnecting anything.
- Connection: Connect the SG-004A leads to the test points. For 4-20mA sourcing, you usually need to break the loop and insert the calibrator in series. For RTD simulation, connect directly to the input terminals.
- Configuration: Select the correct signal type on the dial/buttons. This seems obvious, but double-check. If testing a PT100, ensure the calibrator is set to PT100, not J-Type. Set the output value to your target (e.g., 50% = 12mA).
- Verification: Watch the PLC/DCS input value change. If it doesn’t move, check your series connection. Once verified, slowly ramp the signal up and down to check for linearity errors. Power off the SG-004A before disconnecting leads.
Compatible Replacement Models
- ✅ Drop-in Replacement: FNIRSI SG-004A (Same Model) – The standard unit. No config changes needed.
- ⚠️ Upgrade Path: Fluke 707 – Same function, but 10x the price and better protection. Requires no logic changes, just a bigger budget.
- ❌ Not Compatible: Generic Signal Generators – Avoid cheap function generators meant for audio/RF. They lack the 24V loop power and industrial signal tables you need for process control.
Frequently Asked Questions (FAQ)
Can I use this to power a 2-wire transmitter?
Yes, but be careful. The SG-004A has a built-in 24V supply for loop powering, but its current limit is low. It can power a standard transmitter for testing, but if the transmitter draws too much current or has a short, you might trip the calibrator’s protection. Don’t use it to power heavy loads.Is this accurate enough for regulatory compliance?
Probably not. The SG-004A is a field troubleshooting tool, not a primary standard. Use it to find problems, but if you need to certify a safety loop for an auditor, bring out the calibrated Fluke or Beamex. Always check your site’s calibration standards.Does it simulate 3-wire and 4-wire RTDs?
It handles the electrical simulation fine, but remember that a 3-wire RTD setup relies on lead resistance compensation. The SG-004A simulates the resistance, but you might need to manually adjust for lead wire resistance if your PLC doesn’t auto-compensate perfectly.How long does the battery last?
In the field, usually a full shift. The backlight and the 24V loop power are the battery hogs. If you’re just doing quick checks, it’ll last weeks. If you’re leaving it on to simulate a signal for an 8-hour burn-in test, bring a USB power bank.Can I output custom millivolt signals?
Yes, but you’ll likely have to type them in manually. The SG-004A has tables for standard thermocouples, but if you’re working with some obscure linear millivolt sensor, you’ll be using the direct mV output mode. Just watch the resolution limits.What happens if I accidentally connect it to 120V AC?
You’ll likely destroy the input protection and possibly the main board. This is a low-voltage DC tool. Unlike the premium industrial calibrators, it doesn’t have massive MOVs to absorb line voltage. Keep it away from the breaker panels.
