2 Fluke Calibration

734A DC Reference Standard

However, there is more to a four-cell reference

than four outputs. According to NBS Technical

Note 1239, published by the U.S. National Bureau

of Standards (now NIST) in 1987, four to six

references are required to provide measurement

integrity and redundancy, and to minimize the

number of measurements required. References

must be completely independent of one another.

Otherwise, common elements, such as a power

supply or oven, might affect the correlation of

reference outputs. In addition, with frequent

intercomparisons of four cells, you can detect

when any one of the cells begins to drift beyond

specifications or needs to be repaired.

Each 732B is a stand-alone dc standard with

its own power supply, oven, supporting elec-

tronics and packaging. Each may be purchased

separately, or as a full 734A system, which

includes four 732Bs that slide into a rack-width

enclosure.

A fractional ppm 10 V reference

in your lab

With the 734A, it is remarkably simple to estab-

lish and maintain a fractional part per million

(ppm) primary voltage standard in your labora-

tory. Over time, with frequent intercomparisons

of your four cells, and regular calibrations of one

or more cells, you can reduce the uncertainty of

your 734A by a factor of three.

From 1984 until the acquisition of our 10 V

Josephson Array, the Fluke Calibration Primary

Standards Laboratory maintained its corpo-

rate volt in this manner, reducing the absolute

uncertainty to ± 0.35 ppm traceable to national

standards.

Taking your reference to the workload

Standards laboratory operations have changed.

In the past, people brought their workload to

the standards lab. Today, the functions of the

standards lab are being distributed, requiring

that many calibrations be performed in the field.

The 734A, and its electrically and mechanically

independent 732B Standards, was designed to

meet that need. The voltage reference remains

undisturbed in your laboratory, while at the

same time you can distribute the volt to remote

locations outside the lab. When the unit is

returned to the lab, comparisons can be made to

the reference to determine if a shift has occured

during the transfer. To maintain traceability to

national standards, one cell may be transported

to a national lab or other primary standards lab

for calibration, again, without disturbing the

reference. Each 732B Standard is relatively light,

weighing just 5.9 kg, and its 72-hour battery life

provides ample capacity for long shipments. An

optional external battery extends that capacity

to 130 hours. A special transit case, designed to

hold one 732B and an external battery, simplifies

transport even further.

The 732B can stand up to a lot of abuse. The

inputs can be shorted indefinitely and are pro-

tected up to 1100 V dc, 25 mA, without damaging

the cell or affecting its output.

Ideal support for artifact calibration

Combined with 742A-1 and 742A-10k Resis-

tance Standards, a single 732B makes a tough

and compact artifact calibration support pack-

age for instruments like the 5700A and 5720A

Calibrators from Fluke Calibration or the 3458A

Multimeter from Agilent.

The Fluke Calibration Standards Laboratory offers traceability to its own 10 V Josephson Array,

an intrinsic standard of voltage, and to national standards.