Triple Point Of Water Cells

Features

Easy-to-use primary standard

Low cost

Very accurate

Specifications	5901	5901A	5901B	5901C
Expanded Uncertainty	0.0001°C	0.0001°C	0.0002°C	0.0001°C
Reproducibility	0.00005°C	0.00005°C	0.00005°C	0.00005°C
Dimensions	60 mm OD x 380 mm long, 12 mm ID	50 mm OD x 450 mm long, 12 mm ID	30 mm OD x 180 mm long, 9 mm ID	60 mm OD x 380 mm long, 13.6 mm ID

You should be using this low-cost standard frequently to make sure your SPRTs are in calibration.

The TPW is an intrinsic primary standard that does not need recalibration. It is the most accurate temperature standard you can use, and you can learn to use it in an afternoon.

The ITS-90 assigns the TPW a value of 0.01°C (273.16K). The Hart cells achieve this temperature with an expanded uncertainty of 0.0001°C. If you own an SPRT, you really should have a TPW Cell to get the most out of your thermometer investment.

If you calibrate secondary standards, the TPW is one point you can calibrate by primary fixed-point method rather than less accurate comparison methods. If you’re using a reference thermometer to comparison-calibrate industrial thermometers, you can make sure your reference isn’t drifting by frequently checking it at the Triple Point of Water.

Hart’s original Model 5901 cell is used by many national temperature labs around the world. It has a wide mouth for facilitating freezing of the mantle using crushed dry ice. The rubber foot lets you rest the cell on your ice bath or holding fixture for extra stability and protection while you’re using it.

The Hart Model 5901A is a full-size cell designed after the original NBS cell which had a glass support arm. While the arm does not impact performance in any way, some users prefer this design because it facilitates lifting and carrying the cell. The arm can be used as a hook for supporting the cell in an ice bath. The handle is also used as a McLeod gauge for a strictly qualitative check of trapped air in the cell.

The Hart Model 5901B is a smaller cell that’s easy to handle, accommodates shorter sensors and can be maintained in a smaller ice bath, chilled block or refrigerated bath. Despite this cell’s diminutive size, it is made using the same materials and technology as the larger cells. The 5901B has an expanded uncertainty of 0.0002°C or less and a well diameter of 9 mm.

The Hart Model 5901C is designed like Hart’s original 5901 cell with the exception of the well size, which is 13.6 mm rather than the standard 12 mm. It’s a full 380 mm deep and has an expanded uncertainty of 0.0001°C.

All these cells are cylindrical borosilicate glass filled with highly pure water. The water in the cell is gas free with an isotopic composition equivalent to seawater.

The fact is, no one makes a better performing water triple point cell than Hart. Absolutely no one. It is theoretically and practically impossible to make a more accurate cell, so why pay more, why wait forever to get your cells and why buy from anybody with less capability than Hart? It’s not worth the risk or the hassles.

Ask us about our new water triple point insurance plan. For $100 per year (paid in advance) for up to five years, Hart will replace your water triple point cell if you break it. And our warranty is absolute. We don’t care if it was your fault or if an elephant stepped on it; we’ll give you a brand new one.

We also have baths for maintaining your water triple point cells. Not only will your cells be ready to use when you need them, but they’re much safer if you maintain them in one of our constant temperature baths, especially if you think elephants just might step on them!

Primary Standards