WEIGHT TRANSMITTERS FOR SCALES
Model R1930 RS232 weight transmitter with Auto Cal
The
model R1930 Auto Cal transmitter
is a general purpose weight transmitter with RS232 output and inputs for up to
four load cells. Although intended for matched load cells of the Auto Cal
type, the circuit board is also available with
built-in summing for unmatched load cells.
The R1930 has been optimized for fastest settling
together with high rejection of vibration frequencies; both parameters can
be preset from a built-in menu. Software can also be modified on a custom
basis for different applications.
The Auto Cal advantage
Auto Cal is
a shunt-calibration system that, when used with suitable Auto Cal
load cells can eliminate test weights after the initial calibration. Shunt
calibration is a method of using a resistance in parallel with one arm of the
load cell bridge to simulate a known load. Once the scale is calibrated,
the resistance is switched in and the reading recorded, for use in subsequent
accuracy checks and recalibration. When load cells are manufactured to
tight tolerances they can be interchanged without need for recalibration,
contributing further to the Auto Cal
system.
A major feature of the Auto Cal
system is its ability to compensate for the
variation of gravity with latitude and altitude. A little known fact, the
force of gravity decreases as the distance from the center of the earth
increases. because the earth is spinning, it flattens out towards the equator,
which is 43 km wider in diameter than at the poles. This can cause up
to 0.5% error in scales that are based on force rather than the balance beam
principle - and almost all electronic scales are currently based on force, since
the load cell is a force measurement device. Two corrections are provided
in the Auto Cal
system: the first is applied during calibration and the second is applied
during use. This system allows scales to be calibrated at one latitude and
altitude, and used at any other after the new coordinates are entered. The
correction is within 0.01% anywhere on the earth's surface.
SPECIFICATIONS
