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 Force,Torque & Pressure Laboratory

Force
A 5 MN hydraulic machine is installed in the EMI Force and Torque Laboratory for the calibration of force measuring devices in both ​compression and tension, either with increasing forces only, or with both increasing and decreasing forces. The machine has a range of 50 kN
(5 tonne-force) to 5 MN (500 tonne-force) with a measurement uncertainty, at a 95 % confidence level, of between 0.02 % and 0.05 % of the force applied.

The traceability for the forces applied by the machine is provided by the use of force transfer standards that are calibrated in the force standard machines of other National Metrology Institutes, such as PTB in Germany and NPL in the UK. These force standard machines will be either large deadweight machines, or machines with traceability to a deadweight machine.

Calibrations can be made in accordance with an international procedure standard - such as ISO 376 for force-proving instruments - or with a
procedure agreed with the customer.

A wide range of force measuring devices can be calibrated, with mechanical or electrical indication. A measuring amplifier can be provided, if necessary, for use with strain-gauge force transducers.

Tension fittings are available for the standard metric thread sizes specified in ISO 376, but tension devices with other arrangements can be calibrated if suitable fittings are supplied by the customer (advice is available for the design of such fittings and for the calibration of special-purpose force measuring devices).

It is planned to install a 500 kN machine in 2017 to extend the range of calibration force down to 5 kN (500 kilogram-force).

The Force Laboratory also has a range of force measuring devices that can be used on a customer’s site to measure the forces applied by lower-level force machines, including materials testing machines. The range of force covered is from 50 N (5 kilogram-force) up to 5 MN (500 tonne-force) in compression, and 2 MN (200 tonne-force) in tension.

Torque
The Force and Torque Laboratory has a torque standard machine for the calibration of torque transducers and reference torque wrenches. The value of local gravity has been measured at the location of the machine and calibrated weights are used to apply torques over a range from 0.5 N·m to 1000 N·m with an uncertainty of 0.01 % of the applied value, at a 95 % confidence level. Torque can be applied in both a clockwise and anticlockwise direction, with increasing values only, or with both increasing and decreasing values.

Note:
A torque of 1 N·m is about the same as a torque of 0.74 lbf·ft.
Advice is available on the various calibration procedures related to torque measurements, and on the best method of mounting different types of transducer in the EMI torque standard machine. Reference torque wrenches of capacities 10 N·m, 100 N·m and 1000 N·m can be used at a customer’s laboratory to verify the performance of machines that calibrate industrial torque wrenches.

Pressure
The EMI Pressure Laboratory is equipped with deadweight piston gauge standards that provide a very good uncertainty for the measurement of gas and oil pressures, over a wide range of pressure, in both the absolute and gauge mode. A special pressure standard can also make accurate measurements of small gas and oil differential pressures in the presence of a high line pressure up to 20 MPa.

The local value of gravity has also been measured in the Pressure Laboratory, and the masses, piston gauges and environmental sensors of the reference standards have been calibrated by the Czech National Metrology Institute to provide the required traceability.

The laboratory also has a vacuum calibration system with a vacuum chamber that can be heated to 200 °C and evacuated with a turbo pump to achieve a very low value of absolute pressure of around 2 x 10-9 mbar (2 x 10-7 Pa). Depending on the value, the absolute pressure is measured by Ionising, Spinning Rotor, or Capacitance reference vacuum gauges. These have all been calibrated at PTB in Germany.

The calibration service provided by the Pressure Laboratory is summarised in the following table:

Medium Mode Range

CMC

Gas 

Absolute
0.01 mPa to 1 mPa
1 mPa to 1 Pa
1 Pa to 9 kPa
9 kPa to 14.1 MPa
 
10 %
1 %
0.05 %
0.003 % to 0.008 %

Gas 

Gauge

              -91 kPa to 14 MPa 

0.003 % to 0.008 %
Gas  Differential 0 kPa to 200 kPa 0.004 % + 9 Pa

Oil 

Absolute 0.2 MPa to 500.1 MPa 0.003 % to 0.008 %
Oil  Gauge 0.1 MPa to 500 MPa 0.003 % to 0.008 %
Oil  Differential 0 kPa to 200 kPa 0.004 % + 9 Pa


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