Calibration device

The precision rotameter is a secondary calibration device. If it is to be used in place of a primary device such as a bubble meter, care must be taken to ensure that any introduced error will be minimal and noted. The precision rotameter may be used for calibrating the personal sampling pump in lieu of a bubble meter provided it is (a) Calibrated with an electronic bubble meter or a bubble meter, (b) Disassembled, cleaned as necessary, and recalibrated. It should be used with care to avoid dirt and dust contamination which may affect the flow, (c) Not used at substantially different temperature and/or pressure from those conditions present when the rotameter was calibrated against the primary source, (d) Used such that pressure drop across it is minimal. If altitude or temperature at the sampling site are substantially different from the calibration site, it is necessary to calibrate the precision rotameter at the sampling site where the same conditions are present. 

It is often assumed that the measurements taken with a calibrated device are accurate, and indeed they are if we take account of the variation that is present in every measuring system and bring the system under statistical control. Variation in measurement systems arises due to bias, repeatability, reproducibility, stability, and linearity. 

How do you calibrate devices used to demonstrate conformance of product with specified requirements ... 

Different methods used for calibrating samplers include rotometers, wet-test meters, pressure gauges across fixed orifices, mass flow meters, hot wire flow meters and bubble tubes. Each of these calibration devices requires an appropriate correction factor. Some of the devices measure mass flow rather than volumetric flow. Sampling requires volumetric flow calibration. 

Most of the calibration devices require original calibration by a primary standard. A bubble tube is the only device mentioned that is a primary standard(8). It can be checked with simple laboratory tools. 

One device of this type was discussed by Hickam and Witkowski(23). In the diffusion limited devices that have been discussed, the flow rate of the gas is not normally an important factor. In the Hickam device, however, the gas flow is of paramount importance and new possibilities or complications arise. The structure consists of pump (upstream) and sensor (downstream) cells cylindrically surrounding a flowing stream of gas containing oxygen. The sensor cell EMF is fedback to the pump so that oxygen is either added to or subtracted from the stream in the amount required to keep the sensor EMF at a constant value. For a calibrated device, the amount of pump current required measures the oxygen content of the gas at the inlet of the structure provided the flow rate is held constant. Alternately, if a gas of constant composition were employed, the structure could be used to measure flow rate. 

Fig. 8.3. The pseudo CD signal of calibration device. The cross-points have a CD signal of AA = +1.

A calibration chain B sample treatment, C associated quantities. The numbers indicate the link between steps. TS transfer standard (masses, wavelength calibration devices, etc), RM laboratory or any non certified reference material, CRM certified RM, PCRM primary CRM e.g, pure substances or matrix CRMs certified with a primary method (balance, IDMS etc). RMs and CRMs can be used at various stages of the measurement process. For chain A PCRMs or CRMs do not exist for all substances in particular for organic and organo-metallic determinations. For step 10, 11 and 12, PCRMs or even CRMs rarely exist. For step 6 laboratories may prepare raw extracts to follow the purification stage. 

The field measurements were carried out in coastal and offshore waters south of Cape Cod, New England in July 1997 in the framework of the NSF-sponsored Coastal Ocean Processes study (CoOP97) conducted onboard the RV Oceanus. The main part of the setup combined an infrared camera, an infrared carbon dioxide laser and a temperature calibration device (Fig. 4). 

The analyte concentration in the portion of the sample zone yielding the analytical signal should match the dynamic concentration range of the flow-based analytical procedure. To this end, in-line sample dilution is often required, and this step is efficiently accomplished in a flow analyser. As emphasised in Chapter 1, calibrated devices such as burettes, volumetric flasks and pipettes are not required, as the sample and reagent volumetric fractions are maintained for all of the assayed sample and standard solutions. 

WHAT INFORMATION CAN BE OBTAINED FROM RECOMMENDED CALIBRATION DEVICES ... 

The last device for measuring gas flow and for calibrating mass flow controllers that is discussed in this chapter is called the capillary gas flow measurer. The principle of this device is used in many modem automatic calibration devices for mass flow controllers. The scheme of such a device is shown in Figure 2.18. 

Where practicable, each item should bear a label or tag indicating that it has been calibrated and an expiry date for that calibration. Evidence should be available that the calibrating devices are themselves accurate, or, where contractors have been utilised, that accuracy is guaranteed, for example by NATA certification of the contractor. 

This treatment is simple more complex treatments [4] lead to similar conclusions. Because of some of the assumptions that went into finding Eq. 5.37, we should not assume that we can compute the true velocities from it an empirical coefficient like the orifice coefficient would enter. However, most rotameters arej treated as calibrated devices for a given tube, float, and fluid the Qz curve is measured and thereafter one simply reads the float position and looks up the flow rate from that calibration curve. 

Before each run of observations the adjustment of the Stokesmeter was examined using any bright star. The efficiency of the Stokesmeter is 94-95%, that includes inefficiency of the calibration device. 

Ensure all flow and differential pressure indicators etre zeroed and calibrated. All control room pressure indicators need to be checked with a calibrated gage. All dial thermometers and outside pressure gages should be removed and checked for accuracy. The unsatisfactory ones should either be replaced or removed prior to the test and read with calibrated thermocouples, thermometers, or gages during the test. These calibrated devices should adequately fit in the existing fittings. 

Figure 4.4.17. Description of the principal construction of a Knauer membrane osmometer A 300 1 - head thermostat, 2 - channel for syringe, 3 - calibration device with suction tube, 4 - calibration glass, 5 - c illary position MEASUREMENT, 6 - capillary position CALIBRATION, 7 - tension screws, 8 - cell retaining disc, 9 - upper half of measuring cell, 10 - sample introduction system, 11 -semipermeable membrane, 12 - lower half of measuring cell, 13 -pressure measuring system, 14 - cell thermostat, 15 - suction of calibration bottle. [Reprinted from the operating manual with permission from Dr. H. Knauer GmbH (Germany)].

Remove the dosimeter charger (calibrating device) (refer to Figure S6.1). Most dosimeter chargers will have to be partially disassembled, the battery inserted following the manufacturer s recommendations, and then reassembled. 

Profiles comprise cross sections that are not a circle, annulus, or wide sheet. Like pipe and tubing lines, profile extrusion lines consist of an extruder, profile die, calibration device, cooling system, puller, and a cut-off saw and stacker or wind-up unit. The main differences are the dies and calibration units. Due to lack of symmetry, obtaining a correct cross section in a profile die is difficult. Differential flow resistance in different parts of the cross section alters the flow rate for these parts of the die. In addition, die swell may vary due to the differences in flow. Consequently, the extrudate may bend as it exits the die. To equalize flow, the die land length is varied or restricting plates are used in channels where the flow is too rapid. Many profile dies are split into sections, with the die sliced perpendicular to the major axis. Thus, sections can be altered in the process of die development. Flow simulation software is particularly useful in profile die design. 

Meters require calibration against standard sound sources. Meter suppliers usually offer a calibration device. For most meters the device fits over the microphone and generates controlled sound sources. 

As the appearance is more than the color, it is advantageous that color combined with fabric substrate could be viewed accurately on a calibrated device screen and communicated precisely along the textile supply chain. There are still many textile samples, for example, yam-dyed fabric, which cannot be accurately measured by a spectrophotometer. Therefore, color-and-image systems have been developed for more reliable digital color presentation on various textile substrates. However, these systems need further development. When developed, these color-and-image systems will assist efficient color communication throughout the supply chain (Che and Li, 2010). 

Calibrate each personal sampling pump before and after use with a representative filter cassette installed between the pump and the calibration devices. 

The essential components of a modem Mdss-bauer spectrometer as illustrated in the block-diagram of Figure 5 are the velocity transducer, the wave form generator and synchronizer, the multichannel analyzer, y-ray detection system, a cryostat or oven for low and temperature dependent measurements, a velocity calibration device, the source and the absorber, and a read-out unit. 

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