Tiedown load cells

05dec17

Load cells (top)

locations,history

Picture notes:

At some point td 12 ldc1,ldc2 were switched.

It used to be ldc1 left, ldc2 right (on this picture)
20aug10 it is ldc2 left ldc1 right.. we need to verify the correct number of the load cells.

09jun11

checked that picture td12 is correct. ldc2 closest to cabinet (removed cable at load cell and watched which one went away at little star.
Note: the loadcells at td12 are marked: one closest to box , and 2 farther away. this is reversed from what is really there. Some day we may want to switch the cables at the input to the amps.

Load Cell locations By Date
date	td12-1	td12-2	td4-1	td4-2	td8-1	td8-2
180503 new loads purchased. 372303,372304,372305,372306
171128 (4) installed	260310	90409	90410	260311	260312	253850
171115	failed after 1606 hf run			failed 170829		replaced cable (3)
160317			90410	09458	90407	253850
09jun11 (1)	k147697 (90408)	replaced with?? (90409)	90410	09458	90407	90459
06oct09	147697	replaced with ??	90410	09458	90407
23jun08	147697	207629	90410	90458	90407	90459
14nov06	147697	90409	90410	90458	90407	90459
14aug98	90408	90409	90410	90458	90407	90459
xxjan16 (2)	90408	90409	90410	90458	90407	253850

(1)09jun11 went to td 8,12, checked loadcells:

td12:

load cell 2 is closest to box, load cell 1 is farthest from box.

checked this by removing cable at loadcell and watching which ldcell reading changed at little star.

The loadcell closest to box is marked loadcell 1(on top). This marking is incorrect.

they have labeled td12-1 (90408) td12-2 (90409). I have td12-1 replacing 90408 back on 14nov06 with 147697. I'm going with the 147697.

(2)xxjan16 td8-2 load cell was damaged by the hf transmitter in nov15.

The load cell cable was replaced back in nov15.

(3) 171115

td8-2 cable was broken by hurricane maria. replaced 171115, recalibrated.
td8-1

has had -.200mv offset that can't be removed since at least jun17
tested using same amp,cable with spare load cell (171116). balanced ok.. so td8-1 ldcell needs to be replaced,

td12-1

tested amp, cable with spare load cell (not installed). works ok.. so td12-1 needs to be replaced

td4-2

bad since 28aug17
tested amp,cable with spare load cell (not installed). works ok.. so td4-2 needs to be replaced.

(4) 260310->td12-1, 260311->td4-2, 260312->td8-1 installed. calibrated 30nov17.

Load cell calibration

Load cell calibrationn form (.html) .. fill in when calibrating load cells
Factory calibration pages for each load cell

When load cells were calibrated:

191115 (.pdf) (more info)
190620 (.pdf)

td4 did not have all tension released when calibrated.. redid the next day.

171217

Load cell resistances measured at input to amp. (top)

The wheatstone bridge in the load cells has 4 wires that go to the amplifier in the td box. The are labeled: Ex+,Ex-,Sig+,Sig-. If you remove these cables at the amplifier you can measure the load cell resistance. This is a quick way to check if the load cell is healthy. It also will show problems in the cable from the loadcell to the box and the db25 connector that brings the cable into the box (it contains filters that can blow out).

In the table below:
        amp 1 is the top    amplifier
        amp 2 is the bottom amplifier
        cable 1 normally goes to the top amp
        cable 2 normally goes to the bottom amp
see the drawing in the td manual for where the load cell is located on the yoke.

To do the measurement:

turn off amplifier
remove the 4 wires that go to the amplifier.
remove tension on the load cell by raising the jack. Point the dome point at the tiedown.
measure the resistance at the 4 wires that connect to the amp.
The sparcarrestor,and db25 filter should be in place.

resistance values for loadcell cables at input to loadcell amplifier
td,ldcell,cable	Ex+ to Sig-	Ex+ to Sig+	Ex-to Sig-	Ex- to Sig+	Ex+ to Ex-	In+ to In-	date/notes
4-2.90458	351.2	351.0	351.2	1050.0			01dec17 (in lab after removal)
12-1,90408	352.4	1048.0	350.6	359.0			01dec17 (in lab after removal).
8-1,90407	264.8	265.	265	265	343	356	14nov17. (-200mv offset.. bad)
8-2,253850	268	269	267	267	357	355	15nov17. loadcell ok.
8-2 ,90459	269.33	268.60	268.10	268.70			13jan16 (2)
12-1,90408	267.6	267.9	267.9	267.7			9jun11
12-2,90409	267.5	267.2	268.4	267.5			9jun11
8-1 ,90407	268.1	268.8	268.6	268.6			9jun11
8-2 ,90459	268.8	268.8	268.4	268.5			9jun11

12-1,90408	289.7(1)	268.6	267.6	267.5			09nov06 (1)
12-1,90408	267.9	268.4	267.6	267.9			17jan05

12-2,90409	264.2	264.4	264.5	264.5			09nov06
12-2, 90409	267.1	267.5	268.2	268.1			17jan05

4-1,90401	267.8	268.2	267.8	268.2			02sep05++
4-1,90410	267.3	268.7	267.8 237.4**	267.5			17jan05
4-1,90410,1	268.4	267.7	268.9	270.4			31oct01

4-2,90458	264.8	264.9	264.9	265.1			02sep05++
4-2,90458	264.2	264.3	264.7	264.7			17jan05
4-2,90458	264.5	264.6	264.9	265.0			31oct01

8-1,90407	268.2	269.6 357.6**	268.8	269.7			02sep05 ++ with filter
8-1,90407	268.1	267.9	268.3	268.3			17jan05
8-1 ,90407,1	268.0	268.3	269.1	269.3			31oct01

8-2,90459	268.6	268.6	268.1	268.2			02sep05 ++
8-2,90459	268.7	268.6	268.6	268.3			17jan05
8-2,90459,2	268.5	267.4	268.2	268.3			31oct01
8-2,90459,1 When db25 filter bad	264.2	352.3 **	352.4**	268.2			31oct01

The values with ** had bad filters in the db25 connector.
++ removed the filter because it was bad (and had no spares)

1. 09nov06. ld cell 1 td12 failed. replaced with spare loadcell
2. 13jan16.. load cell had been damaged by hf back in nov15.

could not get the balance to go to 0. tried switching cables at load cell, problem stayed with the load cell.
the load cell cable had been replaced back in nov15.

Load cell amplifiers:

scm5b. data sheet pinouts.

board schematic

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