Service & Support · Calibration tools · Servicing scales since 1974

Quick Calibration

Get the right number into your indicator. Run the numbers below, then follow the steps for your head — 640, 660, Digi-Star or Libra.




Weigh a known load, then correct the number


New custom number
—
Enter all three numbers.

The starting number is a starting point, not a constant. Re-check it against a certified scale a couple more times — it settles within about 1%. Weigh the cart hitched to the tractor, not sitting on the jack stand.

Build the 5-digit Configuration Code Number for a 660







CF9 NuM
07430
Grain cart, 2-1/4 Dual bars, 200,000 × 20 lb.

Enter it under CF9 NuM — the menu path is in the 660 section below. Codes starting 97, 98 or 99 are custom settings and add a CuST.CF9 menu after CF9 NuM.

The .4 method — capacity at 0.4 mV/V



Custom number · lb
36904
kg
16739
Goes in the Libra app as the Rated Capacity, with Sensitivity 0.40 mV/V and Cal Factor 1.00. It is a ratio setting, not your cart’s actual capacity.

Figures from the Avery Weigh-Tronix 660 Custom Calibration Number table. Using a custom configuration means you must verify against test weights or a certified scale.

Capacity at 0.4 mV/V · lb
—
kg
—

For bars that are not on the list. Read the rated capacity and the mV/V output off the cell’s spec plate or datasheet. Every bar under the machine must share the same rated output before the capacities can be added together — check that first, then verify the result against a certified scale.



Your settings

Effective span · lb per mV/V
—
Same as 0.4 mV/V at
—

Compare with another setup — optional

Fill in a second setup to compare the two.

The three Libra fields are one ratio, not three settings: rated capacity ÷ sensitivity × cal factor. Two setups with the same ratio are the same calibration, whatever the individual numbers look like.

Practice — work it out, then check your answer


Work it out, type the number, and press Check.

Score 0 of 0 — the numbers change every time, so run it as often as you like. Nothing is recorded or sent anywhere.

The formula

Every indicator, same maths

Whatever head you run, correcting a scale is the same arithmetic. Only the name of the number changes.

NEW NUMBER = certified weight ÷ weight your scale showed × current number
Indicator What the number is called Where it lives
Avery Weigh-Tronix 640 CUSTOM number alongside the CONFIG number
Avery Weigh-Tronix 660 CUSTOM number CuST.CF9, after CF9 NuM
Digi-Star GT400 and most others CAL number alongside the SETUP number
Agrimatics Libra Harvest / Libra Cart Rated Capacity Device tab, with Sensitivity 0.40 mV/V
Worked example. The truck crosses a certified scale at 58,654 lb. Your cart read 59,240 lb. 58,654 ÷ 59,240 = 0.9901. If your current number was 37,500, the new one is 37,500 × 0.9901 = 37,129.

Weigh-Tronix 660

Current in-cab head

The 660 is set up with a five-digit Configuration Code Number that describes the bars, the capacity, the increment, the print format and the units. Once that is in, a Custom number trims the accuracy.

Getting to the configuration number

  1. Press and hold HOLD / MENU. PASS shows briefly.
  2. Enter the password 3088. SEtuP is displayed.
  3. Press ▼ to Calib, then ▼ to Scale 1, then ▼ to Zero.
  4. Press ▶ through SPAN → LiNEAr → build.UP → INPut → GrAvity → diSPlAy → Cal.UNit → PriNt.
  5. Press ▶ once more — CF9 NuM is displayed.
  6. Press ▼ to see the current code. From the factory it is 05130.
  7. Key in your code and press ↵ to accept.
  8. Press ▲ repeatedly until SAvE No shows, press ▶ to reach SAvE YES, then ↵ to save.
A code starting 97, 98 or 99 is a custom setting, and a CuST.CF9 menu appears after CF9 NuM — that is where the custom number goes. Use the lookup tool above to find it.

Codes for common jobs

Application Weigh bar / cell Capacity × increment Code
Grain cart 2-1/4D 200,000 × 20 lb 07430
Grain cart CC-30 compression cell 200,000 × 20 lb 14430
TMR mixer 2-1/8 in 20,000 × 5 lb 05230
TMR mixer 2-1/2 in 200,000 × 10 lb 09330
TMR mixer 2-1/4D 200,000 × 10 lb 07330
TMR mixer CC-30 compression cell 200,000 × 10 lb 14330
Livestock 2-1/8 in 20,000 × 1 lb 05030
Livestock Chute weigh system 20,000 × 1 lb 15030
Livestock Alley weigh system 2,000 × 1 lb 13330

If you cannot tell which bars are on the system, try one of these and see whether it weighs sensibly, then trim with the custom number. If several codes all read wrong, call us before you keep guessing.

Trimming the custom number

Same formula as everything else on this page. Put a known weight on, compare, and multiply. From the 660 manual: a current custom number of 4,000 with 15,000 lb applied but 10,000 lb displayed gives 15,000 ÷ 10,000 = 1.5, so 4,000 × 1.5 = 6,000. Change it in the Custom Calibration setting under SETUP.

Weigh-Tronix 640

CONFIG and CUSTOM

Weigh-Tronix offers a standard and a custom calibration method. On a grain cart, use the custom method. Almost every indicator bought through Central City Scale arrives calibrated; a grain cart usually needs one final adjustment on the farm.

Building the CONFIG number

For all grain carts the first two digits are 98, under the CONFIG menu.

  • The third digit is the display increment — 3 for 10 lb, 4 for 20 lb, 5 for 50 lb. So 983, 984 or 985 so far.
  • The fourth digit is 9 if you want to use a printer. That gives 9839, 9849 or 9859. Leaving the 9 in does no harm even without a printer.
  • The fifth digit is a zero.

Final CONFIG number: 98300, 98390, 98400, 98490, 98500 or 98590.

Starting CUSTOM numbers

The custom number for calibration is on page 16 of the 640M manual. Note that a Central City Scale three-bar grain cart can weigh out as a four-bar system, because of the resistor in the junction box on some units. Grain cart systems are labelled as 2-1/4 Dual bars.

System How to tell Starting CUSTOM number
3-bar with resistor Junction box has external 5-pin plugs 36,900
3-bar without resistor Wires hard-wired into the junction box 27,680
5-bar Weigh-Tronix No resistor on any 5-bar system 46,130 · CONFIG 98590

The quickest check: stand on the hitch while the cart is hitched to the tractor. It will not read accurately on the jack stand. If the weight is off, run it through the calculator at the top of this page.

Digi-Star GT400 and most other Digi-Star indicators

SETUP and CAL

Digi-Star uses a SETUP number and a CAL number. A typical SETUP number is 127080.

Digit Sets Notes
1st — 1 Weighing dynamic Standard
2nd — 2 Rate of gain 2 is recommended for grain cart weighing
3rd — 7 Increment size 6 = 10 lb · 7 = 20 lb · 8 = 50 lb · 9 = 100 lb
Last three — 080 Capacity in thousands of lb 080 = 80,000 lb. For 100,000 lb use 100

Starting CAL numbers

System SETUP CAL number
3-bar Digi-Star 127080 24,000
5-bar Digi-Star 127080 40,000
3-point with compression cells 127080 24,000

Libra Harvest app & Libra Cart

The 0.4 mV/V method

The Libra app does not use a config number. It uses three fields on the Device tab: Sensitivity, Rated Capacity and Cal Factor.

Sensitivity 0.40 mV/V  ·  Rated Capacity = your CUSTOM or CAL number  ·  Cal Factor 1.00

That is the whole trick: when Sensitivity is set to 0.40 mV/V, the Rated Capacity field becomes the custom number. It works whether you are coming off a Weigh-Tronix or a Digi-Star.

It is a ratio, not your cart’s capacity. This trips people up, so it is worth saying plainly. 27,680 is not what three weigh bars will carry — three 30,000 lb bars hold 90,000 lb. The field is labelled Rated Capacity because that is what Agrimatics calls it, but at 0.4 mV/V the number you type in is doing a different job: it sets the ratio between the signal coming off the bars and the weight on the display. Work it out both ways and you get the same scale — 90,000 lb at the bars’ real 1.3 mV/V is 69,200 lb per mV/V, and 27,680 at 0.4 mV/V is the same 69,200. So do not “correct” the figure to your cart’s real capacity. It is not wrong, and changing it will make the scale read wrong.
  1. Pair the app to the Libra device and make sure units match the numbers you are about to enter.
  2. On the Device tab set Sensitivity to 0.40 and enter your old indicator’s number as the Rated Capacity.
  3. Leave the Cal Factor at 1.00 — always, with this method.
  4. Tap Save Settings, then Zero Scale with the cart empty and confirm.
  5. Weigh a known load and, if it is off, correct the Rated Capacity with the calculator at the top of this page.
Usually you will not need to. Central City Scale calibrates every Libra Cart box before it ships, and a sticker on the unit shows the correct cal number. Only recalibrate if the readings start to drift. If you give us the CAL number or CUSTOM number off your old head, we will have it saved onto the device beforehand.

Calibration codes by cart

Set Sensitivity to 0.4 mV/V and enter the code below as the Rated Capacity.

Equipment mV/V Calibration code
3-bar Weigh-Tronix Libra Cart (resistor) 0.4 36900
3-bar Weigh-Tronix Libra Cart 0.4 27680
5-bar Weigh-Tronix Libra Cart 0.4 46130
6-bar Weigh-Tronix Libra Cart 0.4 55360
8-bar Weigh-Tronix Libra Cart 0.4 73800
CC-50 Weigh-Tronix Libra Cart 0.4 24000
CC-50 / WT Libra Cart pivot style (Kinze) 0.4 48000
3-bar Digi-Star Libra Cart 0.4 24000
CC & 3-bar Digi-Star Libra Cart (Unverferth, Brent, Kinze) 0.4 48000
5-bar Digi-Star Libra Cart 0.4 40000

Bars that are not on the list

Every code in that table is one number per bar, multiplied by the number of bars under the machine. Weigh-Tronix bars without the resistor work out to about 9,226 lb per bar — which is why three of them come to 27,680, five to 46,130, six to 55,360 and eight to 73,800. Digi-Star bars work out to 8,000 lb per bar, so three come to 24,000 and five to 40,000.

That per-bar number is not arbitrary. It is the cell’s own rating scaled down to 0.4 mV/V:

rated capacity ÷ rated mV/V × 0.4 = capacity per bar  ·  × number of bars = the number you enter

So if your bars are not on the list — an odd cart, a rebuilt system, or cells off something we did not sell — you do not need the list. Read the rated capacity and the rated mV/V output off the cell’s spec plate, put them into the Load cell mV/V equivalent tab at the top of this page, and it gives you the same kind of number.

Two things to check first. All the bars under the machine must share the same rated output, or the capacities cannot simply be added together. And a number worked out this way is still a starting point — weigh a known load and correct it before you trust it.

The Cal Factor is a trim, not the calibration

Those three Libra fields are not three separate settings. They multiply into one ratio, and that ratio is the calibration:

rated capacity ÷ sensitivity × cal factor = lb per mV/V

Which is why two setups that look nothing alike can be the same scale. Take a 5-bar Digi-Star cart entered the .4 way — sensitivity 0.4, rated capacity 40,000, cal factor 1.000. That works out to 100,000 lb per mV/V. Now enter the same cart using the real bar specs instead — sensitivity 1.5, rated capacity 150,000, which is five 30,000 lb bars, cal factor 1.000. That is 100,000 lb per mV/V again. Same ratio, same scale, identical readings on the same load. The .4 method is simply the shorter way of writing the same calibration down.

The same arithmetic tells you what a wandering cal factor means. Say a 3-bar Digi-Star cart has the right sensitivity of 0.4 and the right rated capacity of 24,000, but somebody has driven the cal factor to 0.75 to make a load come out right. That is twenty-five percent, and twenty-five percent is not trim. The scale is now behaving as though the rated capacity were 18,000 — so either those are not the bars the capacity assumes, or the load it was calibrated against was wrong. Setting the factor back to 1.000 and finding the real fault is the repair. Leaving it at 0.75 only hides it.

Rule of thumb. Correct the Rated Capacity and leave the Cal Factor at 1.000. A percent or two either way after a check load is ordinary trim. If the factor is heading for 0.9 or 1.1, stop and find out why before you go any further.

The Calibration check tab at the top of this page does this arithmetic for you, and will put two setups side by side to see whether they are really the same.

If a test load comes back slightly off

The app has a calculator built into the Device tab — enter the Certified Reading and the Cart Reading and it sets the Calibration Factor for you. That takes seconds and stays within normal accuracy. For the best long-term accuracy, adjust the Rated Capacity by hand instead, using the calculator at the top of this page, and leave the Cal Factor at 1.00.

Full Libra Harvest manual · Libra Feed manual

Printable guides

PDF

    Numbers still not right?

    Tell us what the head is, how many bars are under it, and what the certified scale said. We have been sorting these out since 1974.

    800.582.3175