TB20, strain gauge weighing module | Edition 1 | 21.12.2018
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10.8
Minimum gaging value v
min
The minimum gaging value v
min
, is the smallest measurement that can be measured without
exceeding the maximum permitted error of the load cell, see data sheets of the manufacturers.
10.9
Scale interval
The scale interval is the resolution of the load cell that lies within the valid error limits. The minimum
scale interval of v
min
is indicated in the respective unit of the load cell. A load cell with the rated load
E
max
= 1,000 kg and a minimum scale interval of v
min
= 0.1 kg has 10,000 parts.
10.10
Precision class according to OIML R60
A classification of the load cells take place in applications subject to and not subject to gaging. For
load cells planned for use in applications subject to classification, the international OIML R60
guideline applies. The classes prescribe a maximum and minimum value for scale intervals d. The
TB20 strain gauge weighing module cannot be gauged. It is not necessary to indicate the precision
class.
10.11
Precision class according to PTB
The European precision classes PTB defines the classes for micro scales, precision scales, commercial
scales, and rough scales.
10.12
Minimum measurement range % of rated load
The minimum measurement range is the minimum measurement range/measurement range interval
a gaging-capable load cell /scale must cover. The TB20 strain gauge weighing module cannot be
gauged. It is not necessary to indicate the minimum measurement range.
10.13
Parallel connection of load cells
When a load can't be mechanically measured at only one measurement point, e.g. a silo on 4
supports, several strain gauge load cells must be used simultaneously. The load cells connected
parallel mechanically can also be connected parallel electrically and connected to 1 TB20 strain gauge
module.
The load cells used for the parallel connection must be coordinated with one another and approved
by the manufacturer.
The current draw of the load cells connected parallel may not overload the TB20 strain gauge module.
10.14
Measurement errors
Measurement errors are mainly caused by the load cells and the connection technology.
Commercially available load cells possess a high degree of precision. Measurement errors usually
occur due to incorrect usage not in keeping with the specified conditions of use.
Measuring line
A voltage drop on the measuring line occurs with 4-conductor connection and/or with poor wiring.
The line-related errors are avoided with a 6-conductor connection.
Due to the very low voltage level in the mV and µV ranges, all lines should be shielded.