PRESSURE & VACCUME CALIBRATION (NABL Accreditation No. C 086)
The primary calibration standards for pressure at IDEMI are the Dead Weight Testers
which use the measurements of force and area to produce a pressure to calibrate
instruments with great accuracy. The force is derived from weight and the area is
that of a piston and a cylinder.
Following table gives the list of Dead Weight Testers used in the laboratory along
with their operational ranges and accuracies. When using the DWTs, corrections for
temperature and variation due to acceleration in gravity (Nominal Pressure x g/9.80665)
are also incorporated.
For low pressure measurements (0.1 – 1.0 Bar) a mercurial manometer of Wallace and
Tiernan make with an accuracy of ± 0.02% of full scale is used. The manometer has
inbuilt setting for temperature and gravity correction.
An electronic standard (Ruska DDR – 6000)
is used for measurement of pressure up to 2000 psig with an accuracy of
± 0.004% of the full scale. Here nitrogen or argon is used as the medium of calibration.
This is a very precision instrument employing quartz bourdon tube as the sensor
adopting the Force Balance Technique. Strain gauge bonded type sensors ( 0 – 1000
psig ) with 3 ½ digits readout are also used with an accuracy of ± 0.05% of F.S.
Digital Pressure Indicator Heise Model 711 of range –1 to 7 kg/cm2 and accuracy
± 0.05% of F.S. is also used for calibration. The laboratory is also equipped with
standard test gauge covering a range from 0 – 3000 kg/cm2 with accuracies of ± 0.1%
to ± 0.2% F.S. The Standard Test Gauges are calibrated with our Dead Weight Testers
calibrated at the National Physical Laboratory, New Delhi.
Dead Weight Tester Calibration
The calibration of Dead Weight Tester is done by using the Cross-Float System. The
dual base system covers a Pneumatic Range (0.25 to 35 Bar) and Hydraulic Range (2
to 1400 Bar). The different subsystems of the DWT Calibration System consist of
the following :
1. Pneumatic Dual Base System Model P7120 with piston cylinder unit of range0.025
to 35 Bar and accuracy class 0.0055% reading accuracy class 0.0055% reading with
traceability to NIST.
2. Hydraulic Dual Base System Model P7300 with 2 piston cylinder (LP/HP) units of
ranges 2 – 70 Bar and 70 – 1400 Bar and accuracy class 0.005% reading with traceability
3. Mass Set : This consists of nominal masses WT3 covering a range up to 100 Bar
and F2 Trim Mass Set.
4. Additional Equipment include the Ruska 2455 – 2470 adaptor kit with 2 float sensor
and RTD thermometer for both hydraulic and pneumatic sections.
5. Ruska 2455 Dead Weight Gauge Monitor with Ruska with Prompt software
6. Precision Electronic Balances Sartorius Make Model LP120005 – 0CE of range12000g
with readability of 0.1 g and Model LP 1200S – 0 CE of range 1200 g with readability
of 0.001 g.
In this method, using the pressure balance between the
Standard Piston and the under Test Piston with known masses the effective cross-section
area of UUT is calculated as a function of different pressures. The actual balance
when floatation occurs is sensed electronically using inductive type sensors, with
a Ruska Cross Float Indicator. The actual masses can be computed with Digital Precision
balances. Thus one can calibrate DWTs by the Primary Cross Float Method. In this
method, using the pressure balance between the Standard Piston and the under Test
Piston with known masses the effective cross-section area of UUT is calculated as
a function of different pressures. The actual balance when floatation occurs is
sensed electronically using inductive type sensors, with a Ruska Cross Float Indicator.
The actual masses can be computed with Digital Precision balances. Thus one can
calibrate DWTs by the Primary Cross Float Method. Corrections applied are for gravity,
temperature, buoyancy fluid density and computations are accomplished using the
Win Prompt Calibration Software. The Win Prompt Calibration Software increases calibration
efficiency by providing full-colour windows-based measurement and also in endowed
with the capability for customizing calibration procedures and reports. The software
stores all the calibration coefficients for working standards, including piston/cylinder
effective area, thermal coefficient of expansion, pressure deformation coefficients
and all calibrated mass values. It includes environmental parameters, including
local gravity, head corrections and ambient air density. It also performs the necessary
calculations of pressure-to-mass and mass-o-pressure in both English and ST units.
The above integrated system for calibration of DWTs affords ease of use, very high
accuracy and precision.
Commissioned very low pressure controller/Calibrator, Make : Ruska, Model : 7250
IP. Range : 0 to 10 InWC & 0 to 30 InWC. with an uncertainty ± 0.02% of reading.
Calibration of Magnehelic Gauges, low pressure Gauges, Manometers, Indicators, &
in low pressure instruments mainly used in pharmaceutical industries etc.
Budenberg Hydraulic Dead Weight Tester Model 380H
0 - 1200 kg/cm2
± 0.05% of the pressure being measured
Budenberg Hydraulic Dead Weight Teste
100 – 3500 kg/cm2
± 0.05% of the pressure being measured
Budenberg Air Dead Weight Tester Model 350A
1 to 1 kg/cm2
± 0.12% of the pressure being measured
Budenberg Air Dead Weight Tester Model 452
0.1 to 7 kg/cm2