ADL3 Internal G sensor calibration

[DarrenR]

I've been working with another ADL3 on the bench, and noticed that it gets really warm if left powered on and connected to Ethernet for say 30 minutes (not sure if Ethernet had anything to do with it, but wanted to note that) The dash was not supplying power to anything external. The G-sensor calibration changed over that time (at 70degF, I zeroed, and sent the configuration; 30 minutes later the dash was 133 degF, and the G-sensors were reading like .17 - .19).

Is it expected that the G-sensor calibration will change with temperature? Can Motec build in a compensation for this?

Any update on support for dash tilt?

Hi David,

Sorry i missed the point of your post last week and focused on the G sensor.
The dash should not get hot unless something is wrong. Maximum temperature should only be 10 to 15deg C above ambiant, unless it is at it's limits for supply currents, then it still shouldn't get as hot as you are seeing.

I have shorted the 5V supply to ground for an extended period and the dash got up to ~60deg C before i noticed. Could something like this be the cause??
Does it happen all the time, or all the time when the ethernet is connected?? Can you tell me how much current the dash is drawing from the power supply/battery?

We will look into adding a temperature compensation to the sensors.

On another note, to add to my previous post, you can do the mounting angle correction in i2 Pro using the following maths-
G Force Long Corrected [G] = 'G Force Vert' [G] * sin('Dash Mounting Angle' [rad]) + 'G Force Long' [G] * cos('Dash Mounting Angle' [rad])

G Force Vert Corrected [G] = 'G Force Vert' [G] * cos('Dash Mounting Angle' [rad]) - 'G Force Long' [G] * sin('Dash Mounting Angle' [rad])

The channel 'Dash Mounting Angle' is a constant setup in i2.

[David Ferguson]

Darren,

Thanks for the replies, and the work on the math to compensate for the tilt. In a few hours, I'll be back at the bench, and can look at the ADL3 some more. It does have a brand new harness, so I suppose there could be a short -- I'll start with verifying supply voltages.

[Holmz]

...
We will look into adding a temperature compensation to the sensors.

That would be good to add, and would take out the majority of the error.

But many of those types of sensors differ (thinking MEMS), so it might be worthwhile to have gain and bias coefficients in a table so users can calibrate their own units.

[David Ferguson]

Just to follow up. My new ADL3 that got hot was due to a short on the 8V supply in the harness. When I shrunk a Raychem junction, I guess I got it a bit too hot, and it caused two splices inside the junction (ground and 8V) to melt their protective heat shrink and short together. All better now, and the unit no longer get's hot when run for a long time.

[chelspeed]

I've done the mod with the corrected g force as in the attachment. Many thanks for posting that. Obvious when someone else has done it and you can copy.....

Made me realise I wasn't sure about vertical G. Is it normal to zero the vertical G when parked. That way it goes negative over a brow and positive in compression through a dip? Or is it normal to have the parked car seeing +1G (as it does really) and <1 over a brow and >1 through a dip? Or perhaps it doesn't matter, whichever works for you.

Can't get my head round the pitch and roll thing yet though. Need to go back 35 years to when I learnt about arc tans.

[DarrenR]

Made me realise I wasn't sure about vertical G. Is it normal to zero the vertical G when parked. That way it goes negative over a brow and positive in compression through a dip? Or is it normal to have the parked car seeing +1G (as it does really) and <1 over a brow and >1 through a dip? Or perhaps it doesn't matter, whichever works for you.

Hi chelspeed,

For the calculations to work you must 'zero' the vertical G so it reads 1G when stationary, so yes the dynamic reading is a +/- of 1G.

It's personal preference if you like vertical G to read 0, but it is technically incorrect.

[Holmz]

Made me realise I wasn't sure about vertical G. Is it normal to zero the vertical G when parked. That way it goes negative over a brow and positive in compression through a dip? Or is it normal to have the parked car seeing +1G (as it does really) and <1 over a brow and >1 through a dip? Or perhaps it doesn't matter, whichever works for you.

Hi chelspeed,

For the calculations to work you must 'zero' the vertical G so it reads 1G when stationary, so yes the dynamic reading is a +/- of 1G.

It's personal preference if you like vertical G to read 0, but it is technically incorrect.

The advantage of doing it "Darren's way" is that you can divide lateral (or longitudinal) G by vertical-G.

Sometimes you see people talk about getting a max lateral G-force of 1.5 ... Maybe some transient can give your a single noisy reading like that.
Also if you going around a banked turn, or through a dip, then the value can be high; but it is generally meaningless quoting some transient numbers.

So normalizing the G with the vertical of ~1.0 might be a bit useful at some point later on.