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QED users => QED users => Topic started by: mylab on Thursday January 9 2020 03:00:16 AEDT AM



Title: THS-B NULL Variance
Post by: mylab on Thursday January 9 2020 03:00:16 AEDT AM
"The THS-B NULL setting can vary by as much as 5 from a very hot day (approx 30+C) to a very cold day (approx. 10 C), so it’s most important to find your NULL point each time you are out detecting. As the box warms up, especially from a cold day, the THS-B NULL point may move, so check it again after around 30 minutes just to be sure. In addition, THS-B NULL may vary between QEDs, meaning that your mate’s QED NULL could be a different number to your own on the same day at the same place."

"For some fellow QED owners 45 is NULL, whereas for others it could be 5 below NULL."



As said above in the latest version of the user manual for the QED PL2 in that a THS-B Null can vary due to weather conditions. And THS-B Null can vary between 2 QEDs even on the same day and at same place.

However for some fellow QED owners their QEDs will always be different as to their THS-B Null position, no matter.

Therefore I am curious why so considering each QED are produced in the same way including their components and even after having the latest upgrade some QED owners will still have that variance of 5 or so difference in their THS-B Null point, no matter?


Title: Re: THS-B NULL Variance
Post by: Goldman on Thursday January 9 2020 08:40:22 AEDT AM
THS-B is temperature dependent.

The THS-B NULL is setup in the workshop as one of the last internal configurations before released from the workshop ready for sale.

THS-B on all QEDs is set to ~50 in the workshop. However during a run of QED manufacturing, which can extend over a period of weeks/months, THS-B NULL is being set on days of different temperatures.

This configuration could occur on a very cold day (especially in the workshop) or a very hot day. Due to the temperature variation at time of configuration the end result is a (natural) variation between QEDs even though all of the software, electronic components and electronic circuits are identical.

This is why I have said to always check your NULL when out and about detecting, especially after first turn on of the day. Your NULL in winter may well be different to your NULL in summer.

Cheers Goldman


Title: Re: THS-B NULL Variance
Post by: Goldman on Thursday January 9 2020 13:05:41 AEDT PM
The history of THS-B is in itself very interesting.

In the very early days of the QED research and development, Howard found that the electronics (a capacitor) drifted in value depending on temperature and introduced noise in the process. So Howard designed a way of ‘nulling’ out the noise (value variance) introduced by the temperature drift. This was initially called “NULL” on the pre production faceplates, see attached photo.

As a result of Howard’s inquisitive nature, and by further experimentation he found that going under the NULL point significantly improved target response on small target. Further experimentation followed and the full potential of this ‘feature’ was soon realised, so Howard added it as a user controlled feature to enable prospectors to bias towards the size targets they were hunting for, either bias down to improve response to small targets or bias up to improve response to larger targets.

Accordingly, in the first production QED (the PL1) this feature was called ‘BIAS’, but was eventually renamed to THS-B, where the B stands for ‘BIAS’.

So as is often the case in science, a workaround evolved into a fully fledged and totally unique QED feature, which worked in the prospector’s favour, one which I’m sure everyone uses to gain improved performance when out hunting for yellow.

Cheers Goldman


Title: Re: THS-B NULL Variance
Post by: WM6 on Thursday January 9 2020 21:40:16 AEDT PM
To get very good temperature compensation, you need to (thick) paint your electronic box
inside with wax (paraffin) or, if there could be extremely hot, even better with hot glue.

Such one coating can take a lot of temperature changing shocks by taking external energy
for its (partial)melting and  solidification (curing) instead for heating board inside.

Of course, if possible, PCB alone can be coated too, by sinking it in melted wax or hot glue.



Title: Re: THS-B NULL Variance
Post by: mylab on Saturday January 18 2020 02:46:28 AEDT AM
  

The THS-B NULL is setup in the workshop as one of the last internal configurations before released from the workshop ready for sale.

THS-B on all QEDs is set to ~50 in the workshop. However during a run of QED manufacturing, which can extend over a period of weeks/months, THS-B NULL is being set on days of different temperatures.

This configuration could occur on a very cold day (especially in the workshop) or a very hot day. Due to the temperature variation at time of configuration the end result is a (natural) variation between QEDs even though all of the software, electronic components and electronic circuits are identical.


I see....so once Howard has outsourced the QED to be manufactured locally in Ballarat by Wiltronics, instead of being manufactured by himself, then the variation between QEDs in the future should not exist?


Title: Re: THS-B NULL Variance
Post by: bugwhiskers on Saturday January 18 2020 07:55:13 AEDT AM
Many components suffer from variations due to temperature. The component (capacitor) that was responsible for the drift has been replaced by this type.

http://www.learningaboutelectronics.com/Articles/What-is-a-NPO-ceramic-capacitor

Specifically this component.

https://au.element14.com/webapp/wcs/stores/servlet/ProductDisplay?catalogId=10001&langId=43&storeId=10184&urlLangId=43&partNumber=8820198

https://au.mouser.com/ProductDetail/Murata-Electronics/GRM3195C1H333FA01D?qs=sGAEpiMZZMukHu%252BjC5l7YXCyUf727gYDxMknt%252B2s4Lo%3D





Title: Re: THS-B NULL Variance
Post by: phrunt on Sunday January 19 2020 07:34:03 AEDT AM
It's great to see such high quality components used in the QED.


Title: Re: THS-B NULL Variance
Post by: Doug on Sunday January 19 2020 13:45:18 AEDT PM
  
Many components suffer from variations due to temperature. The component (capacitor) that was responsible for the drift has been replaced by this type.

http://www.learningaboutelectronics.com/Articles/What-is-a-NPO-ceramic-capacitor

Specifically this component.

https://au.element14.com/webapp/wcs/stores/servlet/ProductDisplay?catalogId=10001&langId=43&storeId=10184&urlLangId=43&partNumber=8820198

https://au.mouser.com/ProductDetail/Murata-Electronics/GRM3195C1H333FA01D?qs=sGAEpiMZZMukHu%252BjC5l7YXCyUf727gYDxMknt%252B2s4Lo%3D


The cap still has a small temp coefficient of  from memory of about 60ppm/deg C.So if the B null is calibrated at say 15deg C and the QED is used say at 35 deg C then the  difference is  20X60ppm=1200 ppm which is fairly significant.
doug ::419::