Control of Classification Equipment

Automatic Reflectance Probes (Classification Center)


The classification center is a full automatic machine, which 

  1. fixes the carcass hanging from the rails.

  2. Inserts 7 probes.

  3. Measures the reflectance profiles

    Predicts wrong measurements by neural network

    Repeats measurements once if one of the first measurements are wrong.

  4. Sets the carcass free.

The 7 probes are mounted on 3 carriages which can be moved vertically and horizontally.

On the upper carriage 2 probes are inserted in in the ham,

on the carriage in the middle 3 probes are inserted in the loin

and on the lower carriage 2 probes are inserted in the forepart of the carcass.


The probes combines the measurement of light reflectance with the measurement of distance to give a profile of reflectance when the probe is pressed through the carcass.


Fat thickness and meat thickness are deduced from the reflectance profiles by use of a combination of mathematics and a neural network.

Known standard deviations


Repeatability s(r)

Reproducibility s(R)


 Danish CC


 1,8 % Lean meat


Known possibilities for error



Error contribution expressed as standard deviation

Knife too small



Blunt knife



Dirty sensor window        
Sensor positioned with wrong angle       
Reflection offset       
Reflection gain error    
Position offset      
Position gain error    
Wrong probe length    
Fixture has slacken



Offset in length measurement, Gambrel ->pig nose



Offset in length measurement, Gambrel ->Foreleg



Offset in length measurement, Gambrel -> pubic bone

Carriage vertical start position offset    
Carriage vertical run-off position offset    
Bacon finder (inductive probe) error     
Photoelectric cell error    
Compressed air pressure too low.    
Compressed air pressure too high.    

Wrong insertion angle

Scale offset error    

Scale gain error


The Danish Meat Research Institute keeps track of the used program version.

The Quality Assurance Program for the Classification Center is described in a Danish manual. 

The Classification Center is not used outside Denmark, so there is no need for a translation of the manual.

The following is an abstract from this manual, used as an example of a QAP.

Daily control

Periodic control

Control of instrument

Control of instrument

 Before use:

Personnel from the abattoir do:

  1. Check signal from inductive probe used to detect the skin/bacon edge. There are 4 inductive probes: 1 on carriage 1 and 3 and 2 on carriage 2. A special set of tools are used for the test, and the probes should react within 2 mm. The CC must not classify if the tolerance is not met.

  2. Each of the 3 carriages has a photoelectric cell. Check the distance at which the photoelectric cell responds. The measured distance must not be less than 20 mm below the value when the photoelectric cell was new. The CC must not classify if the tolerance is not met.

  3. Control of fixture. The carcass is fixed in the CC by a fixture. It's essential that the fixture does not loosen from the trolley. Check that the fixture has not moved more than 5 mm from marks on the fixture hanging. If the deviation is between 5 mm and 10 mm, a total repair of the fixture can be delayed until the next production break. If the deviation is larger than 10 mm then the fixture must be repaired before the CC can be used.

  4. Check of optical probes: Insertion speed and reflection. Time for insertion and withdrawal should be between 1.3 and 2.6 seconds. The reflection in air should be between 0 and 6 on a scale from 0 to 248. If the insertion speed is outside the tolerance, then the probe unit is replaced. If the reflection is outside the tolerance, then the probe is cleaned and the measurement repeated. If the reflection is still outside the tolerances the probe unit is replaced.

  5. Check of pressure of compressed air to CC and to the individual probes. The probes are moved by compressed air. The air pressure must be regulated to the prescribed level before start of classification.

  6. Visual check of knifes on probes. Worn knifes must be replaced before start of classification.

The results from the control are noted on a special form and stored in the logbook.

 Inspectors from the Danish Classification Authority do:

  1. Control of weight meassurement.

  2. Control of Length meassurement

  3. Control of instrument.

  4. Control of logbooks.

  5. Control of marking.

  6. Control of transfer of data from the CC to the central database.


Control of data

Control of data

In-use control

Personnel from the abattoir do:

  1. Assessment of % re-measurements.

  2. Assessment of alarms.

  3. Check of positioning of the probes. 10 pigs 2 times on a shift (8 hours).

  4. Assessment of the classification results.

The results from the control are noted on a special form and stored in the logbook.

The Danish Classification Authority do:


Weekly control of average from each CC versus average for whole country.