Description
The Emerson A6370D is an overspeed protection monitor manufactured by Emerson (EPRO) and forms the core monitoring element of the AMS 6300 SIS (Safety Instrumented System). It is a single-channel, display-equipped speed monitor designed for one purpose: to measure rotational speed from a shaft-mounted transducer with extreme accuracy, compare it against configured safety thresholds, and trip the machine before overspeed can cause catastrophic damage.
The A6370D accepts signals from eddy-current, Hall-element, and magnetic (VR) speed sensors, processes them through high-integrity safety logic, and delivers deterministic trip decisions with reaction times as fast as 12.5 ms. When deployed in the standard three-monitor configuration on an A6371 backplane, it forms a 2-out-of-3 (2oo3) voting architecture capable of SIL 3 overspeed protection per IEC 61508 — the safety ceiling for critical rotating machinery. For power plants, compressor stations, and process facilities, the A6370D is the last and most important line of defence between a shaft and a major mechanical failure.
Application Scenario
In a combined-cycle power plant, the steam turbine’s emergency trip system (ETS) had been modernized around an Emerson AMS 6300 SIS. During a routine overspeed test on one of the two turbine-generator sets, the test revealed that one of the three speed monitors was responding with marginally inconsistent timing — not enough to cause a nuisance trip, but enough to flag a cross-channel tolerance deviation during the 2oo3 vote comparison. The plant’s machinery protection engineer immediately recognized the risk: a missed or delayed overspeed trip during a real load-rejection event could mean overshooting the 110% redline and risking blade or coupling damage.
The team replaced the suspect unit with a verified Emerson A6370D (matching the A6371 backplane and existing A6370D/DP Profibus variant), reloaded the configuration through the USB Type B port, and re-ran the overspeed test. All three monitors now crossed the trip threshold within tolerance, the green “Channel OK” LED behavior was correct, and the 2oo3 vote logic showed clean agreement across the full speed sweep. The turbine was returned to service with full confidence in the overspeed trip integrity. The plant’s reliability director subsequently standardized the A6370D as a qualified critical spare across every turbine and compressor train. The value is clear: in an ETS, you do not get a second chance at an overspeed event — the monitor has to be right, first time, every time.
Parameters
| Main Parameters | Value / Description |
|---|---|
| Product Model | (AMS 6300 SIS – Monitor, 1 Ch Speed, Display) |
| Variant | /DP – same monitor with optional Profibus DP interface |
| Manufacturer | Emerson (EPRO), Germany / USA |
| Product Category | Overspeed Protection Monitor (Speed Monitor) |
| System Platform | Emerson AMS 6300 SIS (Safety Instrumented System) |
| Required Backplane | A6371 System Backplane (handles power + signal routing) |
| System Architecture | 3 × A6370 monitors + 1 × A6371 backplane = one AMS 6300 SIS; 2oo3 voting |
| Sensor Supply | -24.5 V ±1.5 V DC, short-circuit proof, galvanically separated; max. 35 mA |
| Sensor Inputs | Eddy-current & Hall-element: 0–26 V, reverse-polarity protected, limit ±48 V, typ. 100 kΩ |
| Magnetic (VR) Input | Min. 1 Vpp, max. 30 V RMS; typ. 18 kΩ |
| Input Frequency Range | 0 to 20 kHz |
| Measurement Range | 0 to 30,000 rpm (typical) |
| Accuracy | ±0.5% (typical); current outputs ±1% of full scale |
| Digital Inputs (Backplane) | 4, galvanically separated (Test Value 1 / Test Value 2 / Enable Test Values / Reset Latch); Low 0–5 V, High 13–31 V |
| Current Outputs (Backplane) | 2, isolated; 0/4–20 mA or 20–4/0 mA; max. load <500 Ω |
| Digital Outputs (Backplane) | 7, short-circuit proof (Out 1–6 configurable + Channel OK / COK); max. 25 mA |
| Pulse Outputs (Backplane) | 3, open-collector, current-limited, galvanically separated; 0–20 kHz, max. 31.2 V / 16 mA @ 24 V |
| Front-Panel Outputs | 1 × TTL pulse (0–5 V, 0–20 kHz) + 1 × sensitivity output (0–3.9 V) |
| Reaction Time (3000 min⁻¹) | “1x per revolution” mode: 35 ms; “Automatically” mode: 12.5 ms |
| Rotational Direction Detection | < 3 × input signal period + 8 ms; SIL 2 |
| Communication | USB Type B (configuration); RS-485 (max. 32 devices, 38.4k / 57.6k / 115.2k baud); Profibus DP (/DP, max. 31 devices, up to 12 Mbit/s) |
| Power Supply | System via A6371 backplane (+24 V DC); module sensor supply -24.5 V DC |
| Power-Up Delay | 60-second function block after power-up or fault-to-normal transition (COK LED flashes) |
| Safety Certification | SIL 3 (Overspeed), SIL 2 (Rotation Direction); TÜV-certified per IEC 61508:2010, IEC 62061, IEC 61511 |
| Industry Standards | API 670, EU Machinery Directive 2006/42/EG |
| Environmental Protection | IP20 (rack-mounted, per IEC 60529), otherwise IP00 |
| Conformal Coating | HumiSeal® 1B31 EPA; ISA-S71.04-1985 airborne contaminant class G3 |
| Operating Temperature | -20 °C to +65 °C (-4 °F to +149 °F) |
| Storage Temperature | -40 °C to +70 °C (-40 °F to +158 °F) |
| Humidity | 5 to 95% RH, non-condensing |
| Vibration / Shock | IEC 60068-2-6 (0.15 mm / 20 m/s², 58–62 Hz to 150 Hz); IEC 60068-2-27 (100 m/s², 6 ms) |
| Operating Altitude | < 5000 m above sea level |
| Mounting | 19-inch rack, 84HP wide, 3RU high (IEC 60297); card slot Type F48 female (IEC 60603-2) |
| Dimensions (W×H×D) | 211 × 130 × 43 mm (8.31 × 5.12 × 1.70 in) |
| Weight | Approx. 490 g (1.080 lbs), exclusive of packaging |
| Compliance | CE (2014/30/EU, 2014/34/EU, 2006/42/EG), EN 61326-1, DIN EN 50581, CSA CAN/CSA-C22.2 No. 61010-1-04, UL 61010-1 (2nd Ed.), TÜV NORD |
| Status | Active / Available (new surplus, exchange, refurbished) |
