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FLOW CONTROL Valve: (optional)
The Flow Control Valve under the mix chamber will stay closed for 6 seconds (FCV parameter) immediately
following a dispense into the mix chamber. The rest of the time it opens when the sensor is covered, and closes
when the sensor has been uncovered for at least two full seconds (based on DLY parameter).
VERIFYING LOAD CELL FUNCTION
Most Problems are related to LOAD CELL function.
There are several ways to VERIFY that the load cells are functioning properly. The slightest touch on the weigh bin should
result in a change in the readout. If this is not the case, something is wrong. When the light touch is removed, the display
should return to its starting point. If this does not happen, something is interfering with free movement of the cell or the bin.
Make a careful inspection of EVERYTHING around the load cells, the hanger bolts, the weigh bin tray and the weigh bin.
NOTHING should interfere with free movement.
NOTE: It is normal for load cell readout to drift several grams over time and with different temperatures. Since all the
component dispenses are weighed by a single set of load cells, this drift will affect all components equally and, therefore, the
ratio of the components will remain accurate. Empty weight is always TARED so each dispense is accurately measured.
The following observations will verify proper load cell operation:
When the bin is empty, between cycles, the display should read near zero. An error of several grams is not important since
this empty weight reading is "tared" from all dispense readings. The "empty weight" readings should be consistently within 1
or 2 grams of each other.
The addition of several pellets to the weigh bin should result in a change in the readout. 1 gram is about 40 pellets.
Most load cell problems are caused by interference to the movement of the load cell. The load cell must be free to respond
to the weight of a single pellet as well as free to move far enough to record a full 20,000 gram weight deflection. (10,000
grams per cell - 10K cells)
If weight readout is very erratic check for damage to the load cell wires. Check for a pinched wire in the connector.
An over stressed load cell will read high. The top limit is ( 3100.0) for a 200 series or ( 31000) for a 400 or 900 series. A
load cell that was forced or pried upward too far will read ( 0.0).
We supply and replace load cells in matched sets and we always include the mounting enclosures. You may remove the
back plate from the enclosure for visual inspection. It is not safe to remove the load cell itself from the enclosure. To do so
may stress the cell itself.
To OPERATE with DAMAGED load cells in a VOLUMETRIC mode, see KEYPAD, *87, Volumetric mode.
To RECALIBRATE the LOAD CELLS, see the HARDWARE MAINTENANCE section.
If you suspect load cell damage or failure, see: LOAD CELL RAW SIGNAL READOUT.
Load Cell Raw Signal Readout
Press "CE" key to check this RAW number for several seconds.
Load cells put out a very small voltage that varies slightly as the load cell is deflected. This voltage is converted, on the
circuit board, to a pulse train and these pulses are counted for 1 full second to determine a weight load. The software can
handle a range of counts from 0 to approximately 249,850.
A properly operating set of 3 K cells will range from about 55,000 to 120,000; a span of about 65,000 from empty weight
(weigh bin in place), to a full bin weight of 2000 grams. (10 K load cells range about 90,000 from empty to a full 9000
grams). The system will work correctly as long as the empty bin weight readout is between 1 and 149,248. 149,248 is the
highest number that the software will accept for zero weight calibration (see parameters, LCZ). If the number is over this
when you press the ZERO weight key, the display will say (ZERO LOW).
This RAW COUNT number is converted to the proper gram readout, by the software, based on load cell calibration
information.
The RAW COUNT numbers are more useful in diagnosing load cell problems because they bypass the calibration math and,
therefore, bypass any calibration errors that might have occurred.