Description

The Metrix 5485C-006 (often designated as 5485C-006-XXX for integral cable systems) is a rugged, moving-coil velocity transducer designed for continuous vibration monitoring in extreme high-temperature environments up to 375°C (707°F). It is standard equipment on heavy-duty industrial gas turbines, steam turbines, furnace blowers, and exhaust fans where solid-state sensors with onboard electronics would fail.

Part Number & Configuration Breakdown

In the Metrix ordering system, the code structure identifies whether the unit utilizes a removable or integral cable layout:

• 5485C-006 (Removable Cable Version): The baseline 006 output type designates a 200 mV/in/s (7.87 mV/mm/s) calibrated sensitivity with a nominal 135\ \Omega coil resistance. It features a top-mounted, 2-pin MIL-style threaded connector requiring a separate high-temperature Metrix 4850 cable assembly.
• 5485C-005-006 (Integral Cable Variant): If your prefix shows a 005 or similar configuration, the final suffix digits (-006) signify a 6-foot integral armored cable permanently attached to a 200 mV/in/s housing.

Technical Specifications

Field Experience & Engineering Insights

The Self-Generating Principle

Because the 5485C relies on a physical bobbin coil suspended by circular spider springs moving through a permanent magnetic field, it self-generates its voltage signal. This makes it completely immune to power supply fluctuations or noise injected via auxiliary power rails. Furthermore, its native velocity output is significantly better at tracking destructive low-frequency structural shocks and aerodynamic impulses compared to standard accelerometers that require software integration.

Grounding and Shield Separation

• Floating Case Configuration: The internal sensor coil is fully isolated from the outer 416 stainless steel housing block.
• Shield Maintenance: When connecting the twin-conductor flying leads to your monitoring system (e.g., a Metrix MX2034 transmitter or a plant DCS matrix), ensure the cable shield is floating at the high-temperature sensor head. Terminate the shield exclusively at the instrumentation panel ground to prevent ground loops caused by physical voltage potentials across the machine frame.

Recalibration and Field Verification Requirements

• Thermal Aging: Over years of intense thermal cycling inside turbine compartments, the permanent magnets can experience minor magnetic flux degradation.
• Verification Cycles: Metrix recommends checking the sensor’s calibration curve every 3 years using a NIST-traceable shaker table set to 1 ips peak at 150 Hz. While the strict factory tolerance is \pm 5\%, field verification limits allow up to \pm 10\% drift before unit replacement is mandated.

Frequently Asked Questions

Can I shorten an integral armored cable if it’s too long for the layout?

If you are dealing with an integral cable version, the flying leads can be clipped and terminated into a local junction box. However, you must execute the termination with extreme care using high-temperature terminal blocks. Never splice or solder the wires mid-run inside a hot turbine enclosure, as thermal degradation will warp the loop resistance metrics and skew the vibration telemetry.

What causes a sudden “Sensor Failure” or open circuit reading on the monitor?

Isolate the loop and read the DC resistance across the two active sensor leads using a multimeter at room temperature. For the 200 mV/in/s (006) version, the internal coil should measure roughly 135\ \Omega (\pm 10\%). If the meter reports an open circuit (OL), the internal micro-wire springs or the armored connection lead has fractured due to excessive structural vibration or physical stress during routine maintenance.

Do I need an intrinsic safety barrier for Div 2 / Zone 2 locations?

No. The Metrix 5485C is officially approved for use in Division 2 and Zone 2 hazardous areas without the installation of galvanic isolators or Zener diode barriers, provided it is wired according to the factory’s non-incendive documentation. If routing the sensor into a Division 1 or Zone 0 explosive environment, an approved safety barrier is strictly required.