INSPECTION OF NON-AUTOMATIC SCALES
VISUAL INSPECTION:
- Whether the scale is subject to inspection first or requires type system approval
- Control of metrological properties (Max, Min, e, d)
- Control of marks and stamps.
MEASUREMENT TECHNIQUE INSPECTION:
- Error Limits Calculation,
- Control of the Zeroing Mechanism:
(If there is no Zeroing Mechanism)
Before starting the examination, the scale must be set to “0” position. In order to bring the digital display scales to zero, a load of 0.1 d should be placed on the scale so that the scale skips the following graduation interval from the “0” zero position. After this process, a weight of 0.5 d is moved back. Digital scales with a zeroing mechanism must have a special signal on the display. and this deviation should be 0.25 d. The zeroing area must be £ 4%.
Checking Repeatability:
To check the repeatability, two weighings must be carried out.
*with a load of 0.5 Max and,
*Max. Weighing the scale should be carried out 3 times on class III-IIII scales and 6 times on class I-II scales with a load of 1000-2000 capacity.
Read the scale in loaded and unloaded conditions. If there is a deviation from zero among the weighing results, the scale must be brought back to zero.
If the scale has an automatic zeroing device, this device must be open during the examination.
The difference as a result of these measurements Pmax – Pmin =DP £ must be AHS.
Corner Load Control
In scales equipped with the Automatic Zeroing Device, this device should not work.
Here, a load corresponding to 1/3 of the maximum capacity is placed on it. Checking by loading the load carriers separately in 1/4 pan on a pan divided into 4 is a must.
If the load carriers have more than 4 loading points on the scale;
In scales with n>4 loading points, each point is brought with 1/(n-1) load.
Accuracy Control:
5.1 Standard Load Control
The scale is loaded with etalon weights by increasing and decreasing (from zero to max, from Max to zero) at at least 5 loading points from “0” to its maximum capacity. This loading Min and Max. should also include the load. In this inspection, such inspection points should be selected so that the inspection error limits change.
For rolling loads, this is done with a load that does not exceed 0.8 of the maximum load.
5.2 Control with Additional Load
5.2.1. Control with the Fully Staged Method
In the control of scales with a maximum capacity of over one ton, other fixed loads can be used instead of the weights to be used. In order for this fixed load to be used as an etalon weight, it must be at least 1 ton or 50% of the maximum load to be used in the adjustment of this weight.
If the measurement error is not greater than 0.3 e at the end of the repeatability control, the load ratio to be used can be reduced to 35% of the maximum load.
If the repeatability control is not greater than 0.3 e. At the end, if the measurement error is not greater than 0.2 e, the load rate to be used can be reduced to 20% of the maximum load.
This Spare Load is Found as follows
First, the Scale is reset. Then the etalon weights are placed on the scale. The value on the display is read. The difference between the value of the etalon and the indicator is a reserve load loaded onto the scale. Then, weight equal to the etalon deviation error is added to this spare load. Then, an etalon load is placed next to this spare load. In this way, maximum load is reached. Then it decreases backwards.
Sensitivity Control
6.1 Threshold Exceedability (Reaction) Control
This examination is performed at “3” points. 1-Min. At 2-0.5 Max 3-Max load, the indicator should change until 1.4 d of load is added at the latest.
6.1.1 Non-Self-Balancing Scales
There should be visible movement on the display until an additional load of 0.4 of its MHS is applied at 3 points.
6.1.2 Self- or Semi-Self-Balancing Scales
6.1.2.1 Scales with Analog Display
Until a load equal to MHS is added at 3 points, there should be a permanent movement on the display at a maximum of 0.7 of the inspection error limit.
6.1.2.2 Digital Scales with Indicators
Until an additional load of 1.4 d is applied at 3 points, the indicator must rise by 1 d.
Finding the Analog Value by Adding Weight
This is the determination of the point when the digital indicator (I) jumps to the next value. is done by the method. The value of (I) in the indicator obtained for a certain load is written. Weights up to approximately 0.1 are gradually added to the pan. This additional load is the value placed until the moment it starts to fluctuate (go back and forth) between the detected indicator value (I) and the next value. The value of this additional load is (L). This measurement error (E) is calculated as follows.
E= (I + 0.5 e) – (L + DL)
E= I + 0.5 e – DL – L
For Example:
Inspection Constant (e) = 2 .0 kg
Loaded Etalon Weight L = 1 500.00 kg kg
Detected Indicator Value. I = 1 502.0 kg
Additional Load at Valuation Point DL = 1.4 kg
Sum of Measurement Error;
E = I + 0.5 e – DL – L
E = 1 502 kg + 0.5 . 2 kg – 1.4 kg – 1 500 kg = + 1.6 kg
This is equivalent to the Analog display. For P, L = 1 500 kg Inspection
P = L + E = 1 500 kg + 1,6 kg = 1 501,6 kg