Installing digital load cells is mechanically much like installing analog ones. What changes is everything around the cable: the power supply has to be clean, the addresses have to match the junction box markings, and corner correction becomes a calculation you enter rather than metal you remove. This guide follows a 120 tf weighbridge from wiring to corner adjustment.
Equipment in common use
Digital cells: BTA-D 30 tf and DHM9B 30 tf (USCells), KDS-D 30 tf, VLC-121D 30 tf (VMC), HM9B-D 30 tf (ZEMIC), ZSFB-D 30 tf (AMCells, MKCells, Keli), LU-D 30 tf (MKCells), C16i (HBM), PDX (Mettler Toledo).
Indicators: DS1M, DS3M, Di01 (MKCells), D2002E, D2008FA (Keli / MKCells), D30, IND780 (Mettler Toledo), DIS2116 (HBM).
Cable and wiring
Running and terminating the cable is the same job as with an analog cell. The colour code below covers BTA-D, KDS-D, VLC-121D, DHM9B, HM9B-D and ZSFB-D.
| Wire | Function |
| Red | Supply + (+12 V DC) |
| Black | Supply − (GND) |
| Green | Signal + (RS-485 +) |
| White | Signal − (RS-485 −) |
| Yellow | Shield (earth) |
MKCells LU-D uses a different order — green, black, white, red. Check the cell label rather than assuming.
Four rules about the power supply
- Use a linear supply — a transformer-based one. Avoid switching supplies: the high-frequency content puts large spikes on the line and endangers the electronics.
- Voltage must be stable and quiet. Direct 12 V DC with output current ≥ 800 mA; 1000 mA is the recommended figure.
- Working range is 7–15 V, with 12 V recommended.
- Wire carefully, and if something is connected wrongly, correct it immediately.
Worked example: a 120 tf static weighbridge
Eight BTA-D or KDS-D cells rated 30 tf each give a theoretical maximum of 240 tf. For safety the bridge is always used at 120 tf. The division would normally be 50 kgf, though customers often ask for 20 kgf or even 10 kgf.
Analog and digital cells alike are built and connected to common standards — GB/T 7723-2002 for truck scales, GB/T 14249.1-1993 for safety requirements and GB/T 14249.2-1993 for general technical conditions — or to the OIML recommendations.
1 Position the cells by address
Fit cells with addresses #1 through #8 at their matching corners. Laying them out this way makes axis-by-axis corner correction far easier later.
2 Land the cables in the digital junction box
Land each cell on the terminal whose number matches its address. Getting this right now saves a long afternoon later.
3 Run the cable from junction box to indicator
4 Confirm addresses and cell count
Where corner error comes from
Before correcting anything, it helps to see where the error originates. In diagram (A) the cell sits square and there is no corner error. In (B) it is tilted by 5 degrees, and the force the cell actually feels is larger than the load applied:
F′ = (1 ÷ cos 5°) × F
At F = 30,000 kgf: F′ = 1.0038 × 30,000 = 30,114.6 kgf — an error of 114.6 kgf.
At F = 5,000 kgf: F′ = 1.0038 × 5,000 = 5,019 kgf — an error of 19 kgf.
Rocker-type cells are built so the load passes through a ball or rocker element (C), which allows movement without letting the cell bend or sag — that is how the error is kept small in the first place.
Correcting the corners
A Enter the indicator settings: division, number of cells, maximum capacity.
B Set the zero point with no load.
C Place the load at the centre of the bridge to establish the reference value.
D Work round the corners one at a time.
E At each corner: if the indicator reads higher than the centre reference, reduce that cell’s correction factor; if lower, raise it. Every digital cell exposes a correction factor you are allowed to change.
The correction formula
K′ = (1 − E ÷ L) × K
where L is the applied load, E the corner error, and K the initial correction factor. Note that K starts at 1.0000.
Correcting by axis rather than by individual corner — possible when the cells were laid out as recommended above — follows the same procedure and halves the walking.
A worked correction
With a 10 tf load moved round the eight corners, the indicator reads:
| Cell | Reading | Error E | New factor K′ |
| No. 1 | 10002 | +2 | (1 − 2÷10000) × 1.0000 = 0.9998 |
| No. 3 | 9998 | −2 | (1 + 2÷10000) × 1.0000 = 1.0002 |
| No. 4 | 9996 | −4 | (1 + 4÷10000) × 1.0000 = 1.0004 |
| No. 2, 5, 6, 7, 8 | 10000 | 0 | no change |
Enter the new factors in the indicator — or let it calculate them, since every digital indicator has an automatic routine. Where the corner errors are large the process repeats several times, and the automatic routine correspondingly takes longer.
Where digital cells earn their cost
High-precision measurement and control
Analog accuracy is limited; digital cells go where it is not enough — steel, copper, precious metals, cotton.
When you cannot apply a real load
On a large oil tank there is no way to place a calibration weight. Digital cells still allow accurate calibration without one.
Fraud resistance
The data is encrypted. Connecting a tampering device either fails outright or triggers an alarm from the cell.
Two faults you will meet
Unstable display. Look at the power supply first — excessive noise on the line is the usual cause.
Error code on the display. Check the communication settings and the bus wiring.
Installation note
KALA Technical Notes
Corner factors that will not settle usually point at the mechanical installation rather than the cells — a tilted mount, a check rod under tension, or a bridge touching its surround. Send us your eight corner readings with the applied load and we will tell you whether the numbers are correctable or the mounting needs attention.
● Digital load cells, junction boxes, linear power supplies and matched indicators.