Omega Engineering OMB-DBK-34A, User Manual

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One Known Temperature Environment
Suppose that you only have one known temperature environment, such as an ice bath. In this case only one
parameter in the “mx + b” equation can be determined for system calibration. This is called single-point
calibration. Since this is normally the largest source of error, single-point calibration is used to correct the
offset.
Using the same information as in the first example, and supposing that the only actual reading available is
called RA:
RA = 2.1°C
Since this reading was supposed to be 0°C, call the correct reading RC:
RC = 0°C
Substituting these values into the mx + b equation results in:
RC = 0 = m (2.1) + b
In a single-point calibration, it is assumed that the value of the scale parameter is completely accurate; that
is, m = 1. Using this information in the above equation results in:
0 = 1(2.1) + b,
b = -2.1
These are the scale (m = 1) and offset (b = -2.1) values that should be entered into DaqView.
Use of a Temperature Calibrator
Occasionally, it is impractical or difficult to get physical temperature references for system calibration. The
temperature region of interest may be far removed from the example temperatures of 0°C and 100°C.
Accurate temperature baths may not be available.
In these cases, you should use a temperature simulation instrument that lets you dial in your thermocouple
type. The simulator should also let you set the two calibration temperatures that are correct for your
application. The calibrator then generates milli-volt signals into the DBK19 card (or other temperature
measurement product). These signals correspond to those that would be generated, by the chosen
thermocouple types, at the selected temperatures. A disadvantage of this approach is that thermocouple
errors are not corrected or compensated.
For many applications, where the thermocouple is used at lower temperatures, a single-point calibration is
sufficient. In general, thermocouples have little error at 0°C. The thermocouple error tends to increase
linearly as the temperature increases.
CE Compliance
The European Union (EU) first developed CE standards in 1985. The standards include specifications for
safety and for EMI emissions and immunity. Now, all relevant products sold in Europe must meet these
standards.
Although CE compliance is not required in the United States, the standards are often adopted by U.S.
companies since they improve product safety, reduce noise, and minimize ESD problems.
In contracted and in-house testing, most LogBook and Daq device products met the required specifications.
Others were redesigned to meet compliance. In some cases, alternate product versions, shield plates, edge
guards, special connectors, and add-on kits were developed. The section entitled
CE Enhancements for
Existing Products , which is located at the end of this chapter, includes examples.
CE-compliant products bear the “CE” mark and include a Declaration of Conformity
stating the particular specifications and conditions that apply. Test Records and
supporting documentation that validate compliance are kept on file at the factory.
DBK Option Cards and Modules
886995
Signal Management 1-15