Tour NTPL Primary Lab

NTPL - Isotech's Calibration Laboratory

Northern Temperature Primary Laboratory

Lab News: Smaller Uncertainties for the Cal Lab
Isotech’s Northern Temperature Primary Laboratory (NTPL) achieves even smaller uncertainties, again!
A purpose of NTPL is to inter-compare fixed point cells and to calibrate SPRTs. SPRTs have definite limitations due to variations in the oxide state of the platinum. Changes of up to 1mK occur at the water triple point temperature after large temperature excursions of an SPRT. Reference Isotech Journal of Thermometry Vol 5 Issue 1. However if an SPRT is used over a limited range, from minus 40°C to plus 30°C it can remain very stable. In reviewing our uncertainties we felt it was worth reducing the uncertainties at the Mercury Triple Point, the Water Triple Point and the Gallium Triple Point, since calibrations with uncertainties smaller than 1mK can be maintained. Our new UKAS Schedule, 31st March 04, reflects our desire to offer clients the best service available. At Mercury, Water and Gallium Triple points NTPL have uncertainties second only to NIST

View UKAS Schedule

Tour the Secondary Laboratory

Laboratory Training

First, NTPL's Henry Sostmann Room

Our primary standards, fixed point cells are located here with their apparatus.

First Stop

Our data gathering centre with two Isotech TTI 3 measuring instruments. The TTI 3 gives us an uncertainty of +/- 0.000,020°C. We also have an Isotech TTI 2 and an ASL F900 Bridge. All fully computer controlled

Next Stop

The TTI 3 is used with our extensive bank of Wilkins standard resistors. These resistors are held in our Standard Resistor Maintenance bath, model type 455.

WTP Cell The laboratory has just achieved outstanding uncertainties for 25 Ohm resistance measurement of +/-0.066ppm (2 Sigma). Our uncertainty for 25 Ohm generation of +/-0.061 ppm (2 Sigma) underpins our temperature measurements which have very low uncertainties.

Next to the Standard Resistor bath we have two Water Triple Point Baths, model type ITL-M-18233. It is in the same wooden cabinet as the Resistor bath. We require two maintenance baths as we are constantly calibrating Isotech manufactured Water Triple Point Cells.

In the bath are our water triple point cells, the uncertainty for our primary reference cell calibrated at NIST is +/-0.000,058°C at 2 sigma, our WTP UKAS accreditation for cells is now +/-0.07mK (2 Sigma).

Next Stop: Gallium Standards

A new plateau - all day, every day. Recently enhanced the Gallium Apparatus Model ITL-M-17401 is now fully automated. The Gallium is 8 x 9 pure.

Our Ga Cell UKAS accreditation is +/-0.000,070°C at 2 sigma, and our Primary Standard Gallium Cell intercompared at NIST realises the Gallium point to +/-0.000,055°C (2 Sigma).

Next Stop: The Mercury Triple Point

The cell is made from 7 x9+ Pure mercury with a proven 20 year stable performance. UKAS uncertainty +/-0.00022°C at 2 sigma.

Next Stop: Indium thru Silver

Fixed point cells are used in our range of superior dual furnaces. They have a heat pipe for temperature uniformity around the cell and a separate annealing furnace for conditioning of the the thermometers to be calibrated.

Our Primary set of reference cells have been intercompared at NIST and NPL and are open cells where we can measure the internal gas pressure and set it to 1 Bar when realising the fixed point. We also have a set of secondary sealed reference cells which are compared to our open cells every year.

Point	Temperature	Uncertainty
Indium	156.5985°C	0.000,325°C
Tin	231.928°C	0.000,300°C
Zinc	419.527°C	0.000,450°C
Aluminium	660.323°C	0.0015°C ^*
Silver	961.78°C	0.00325°C ^*

UCT, 1 sigma

Last Stop

We have many standard thermometers and much more equipment, see our schedule for full details. Our comparison calibration baths are located in a different building.

We have an extensive reference library which is important to our constant research and development.

Have you visited our comparison lab?