METRIXHIGH TEMPERATURE VELOCITY TRANSDUCER

1. PURPOSE PURPOSE 

The purpose of this safety manual is to establish the safety aspect of the Metrix - 5845C High Temperature Velocity 

transducer and to enable the integration of this device into a safety related system, with the objective to be in compliance 

with the requirements of the IEC 61508-2 Annex D. The information contained in this Safety Manual are valid for the model 

indicated in the paragraph 4.1. 

When the 5845C High Temperature Velocity transducer is in included in a Safety Instrumented Function, the integrator shall 

evaluate the performance of the device into the SIF loop, in order to ensure its proper implementation. 

2. TERMS, DEFINITIONS AND A TERMS, DEFINITIONS AND ABBREVIATIONS REVIATIONS REVIATIONS 

2.1. TERMS AND DEFINITIONS TERMS AND DEFINITIONS 

Architecture 

Arrangement of hardware and/or software elements in a system. 

Architectural constraint 

This reports the maximum SIL achievable based on the SIF’s subsystems architecture alone. This is calculated solely on 

the basis of Type A or Type B device selection, redundancy (hardware fault tolerance), and the safe failure fraction 

(calculated or conservatively assumed if no data is provided). It does not pertain to Systematic Capability or 

certification. This is calculated as indicated, using respective IEC 61508 or IEC 61511 tables. 

Architectural Type 

- Type A equipment or (sub)system: “Non –complex” (sub)system or equipment according 7.4.3.1.2 of IEC 61508-2; 

- Type B equipment or (sub)system: “Complex” (sub)system or equipment according 7.4.3.1.3 of IEC 61508-2. 

Diagnostic Coverage 

Fraction of dangerous failures rates detected by diagnostics. Diagnostics coverage does not include any faults detected 

by proof tests. 

Mean Repair Time 

Expected overall repair time 

Mean Time to Restoration 

Expected time to achieve restoration. 

Mode of operation 

Way in which a SIF operates which may be either low demand mode, high demand mode or continuous mode: 

• Low Demand Mode: mode of operation where the SIF is only performed on demand, in order to transfer the 

process into a specified safe state, and where the frequency of demands is no greater than one per year;

• High Demand Mode: mode of operation where the SIF, is only performed on demand, in order to transfer the 

process into a specified safe state, and where the frequency of demands is greater than one per year; 

• Continuous Mode: where the mode of operation where the SIF retains the process in a safe state as part of normal 

operation. 

MooN 

SIS, or part thereof, made up of “N” independent channels, which are so connected, that “M” channels are sufficient to 

perform the SIF. 

Hardware Fault Tolerance 

A hardware Fault Tolerance of N means that N+1 is the minimum number of faults that could cause a loss of the safety 

function. In determining the hardware fault tolerance no account shall be taken of other measures that may control the 

effects of faults such as diagnostics. 

Probability of dangerous Failure on demand PFD 

Average probability of dangerous failure on demand.

Probability of dangerous Failure per Hour PFH 

Average probability of dangerous failure within 1 h. 

Proof Test 

Periodic test performed to detect dangerous hidden faults in a SIS so that, if necessary, a repair can restore the system 

to an “as new” condition or a close as practical to this condition. 

Safe Failure Fraction 

Property of a safety related element that is defined by the ratio of the average failure rates of safe plus dangerous 

detected failures and safe plus dangerous failures.

Safety instrumented function (SIF) 

Safety Function to be implemented by a safety instrumented system (SIS) 

Safety instrumented system (SIS) 

Instrument system used to implement one or more SIFs. 

Safety Integrity 

Ability of the SIS to perform the required SIF as and when required. 

Safety Integrity Level (SIL) 

Discrete level (one out of four) allocated to the SIF for specifying the safety integrity requirements to be achieved by 

the SIS. 

Safe State 

State of process when safety is achieved. 

Systematic Capability 

Measure (expressed on a scale of SC 1 to SC 4) of the confidence that the systematic safety integrity of a device meets 

the requirements of the specified SIL, in respect of the specified safety function, when the device is applied in 

accordance with the instructions specified in the device safety manual. 

λ 

Failure rate (per hour) of a channel in a subsystem. 

λD

Dangerous failure rate (per hour) of a channel in a subsystem. 

λS

Safety failure rate (per hour) of a channel in a subsystem. 

λDU

Dangerous undetected failure rate (per hour) of a channel in a subsystem. 

λDD

Dangerous detected failure rate (per hour) of a channel in a subsystem. 

functional safety 

part of the overall safety relating to the EUC and the EUC control system that depends on the correct functioning of the 

E/E/PE safety-related systems and other risk reduction measures 

safe state 

state of the EUC when safety is achieved

The Metrix 5485C is a moving-coil velocity transducer, specifically designed for continuous use 

in elevated temperatures. A permanent magnet moving back and forth within a coil winding 

induces and electromagnetic field in the windings. This electromagnetic field is proportional to 

the velocity of oscillation of the magnet: the magnet shall be mounted on the vibration object 

to measure its velocity. 

A zero-friction coil suspension provides accurate, repeatable vibration measurements over a 

wide range of amplitude and frequency and is built to withstand the high-g environments and 

cross-axis vibrations typical of gas turbines. The coil bobbin is suspended by two non-twisting, circular spider springs that 

provide a clean frequency response. 

Purely viscous electromagnetic damping is employed and eliminates friction-prone air damping. This allows improved 

detection of small vibration amplitudes at low frequencies. 

The sensor is available in two configurations: with integral armored cable or removable armored cable via a 2-pin MIL-style 

threaded connector. The case is constructed of stainless steel and its robust internals are hermetically sealed to ensure 

durability in the most hostile environments. The product is approved for use in Zone 2 / Div 2 hazardous areas without use 

of intrinsic safety barriers. It is also approved for use in Zone 0/1 and Div. 1 areas with use of an appropriate intrinsic safety 

barrier. 

The Metrix 5485C Velocity Sensor shall be used in application where there is a continuous vibration of the unit to be 

supervised and where the target is the vibration detection over the assigned threshold. 

PRODUCTS FAMILY PRODUCTS FAMILYIDENTIFICATION IDENTIFICATION IDENTIFICATION 

This Safety Manual is valid for each product listed in this paragraph. In the following table are listed the family models for 

the sensor 5485C with Removable Cable. Each sensor is differentiated one from the other by the internal coil resistance: the 

latter allows a differential measure sensitivity. 

SAFETY PARAMETERS SAFETY PARAMETERS 

Specific activities necessary to investigate and reach a judgment on the adequacy of the functional safety achieved by the 

E/E/PE safety-related system or compliant items (elements/subsystems) has been conducted by an independent assessor. 

The following failure rates data shall be used to the PFDAVG estimation, taking into consideration all parameters such as 

redundancy, architectural constraints, diagnostic capability, also introduced by the whole system, including the 

considerations about the proof test and its effectiveness, mean time of restoration, up to the maintenance capability and its 

minimum characteristics. 

NOTICE 

The design of each Safety Instrumented Function shall meet the requirements listed in the reference 

standards that shall be selected by taking into account the specific application.

The estimated safety integrity, for each safety function, due to random hardware failures (including soft-errors) and random 

failures of data communication processes. The following table shows the failure rates of the device listed in para. 4.1. 

NOTICE 

The failures rates are distributed considering the ability of the SIS logic solver to detect short circuit and 

open circuit, as described in para. 7. 

REQUIREMENTS FOR IMPLEMENTATION INTO A SIS REQUIREMENTS FOR IMPLEMENTATION INTO A SIS 

The SIS logic solver shall be able to detect the sensor fault through its signal. The most critical failure modes, open circuit and 

short, give as a result an output signal equal to zero. 

The logic solver used to acquire the 5485C output signal shall have a high internal impedance (not less than 100kΩ). 

In order to maintain the safety capability of the sensor, the logic solver shall activate a proper feedback when a zero-voltage 

signal is detected. This proper feedback shall be used as fault condition of the sensor. The fault condition shall be properly 

managed as per each specific safety function. 

NOTICE 

The sensor isn’t designed to impulsive vibration. It shall be used in application having a natural vibration 

frequency in the range of the sensor in order to allow a proper diagnostic of the correct functionality of the 

sensor. 

NOTICE 

The natural vibration of the equipment under control shall not exceed the transducer maximum 

displacement of 1,8mm (70 mils). 

After the first installation, and after any replacing or proof test, the right functionality of the sensor through verifying of coilto-case insulation. The electrical test shall be used to discover possible wire damage able to increase the resistance of the 

connecting cable. 

PROOF TEST PROOF TEST 

The proof test is not necessary, since for the entire lifetime, the correct functioning according to the specifications indicated 

in the para. 4.2 are satisfied. However, the proof test can be performed in order to satisfy the requirement coming from the 

demand rate of the Safety Instrumented Function, where the Metrix 5845C is involved. 

SENSOR VERIFICATION CALIBRATION PROCEDURE 

Mount the 5845C on a shaker table and verify the RMS output per table below. The table is divided according to the 

different types of Sensitivity. 

NOTICE 

The test detailed in this paragraph shall be carried out by competent and trained personnel. 

WARNING!

Maintenance may compromise the sensor. Follow the instruction listed into the user manual is mandatory

to ensure the correct operability of SIS.