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Inconsistancy in LCRmtr V300 input offset adj I/U

Equipment, circuits, projects, procedures

Postby Guest » Tue Feb 04, 2014 12:00 am

I noticed that there is an inconsistancy in the assisting texts, popping up prior to the actual (I and U) Input offset adjustment actions, ie: In the procedure called Inp Offs Adj I the terminals are prompted to be open and in the proc called ...U the terminals should be shorted, according to the pop-ups. Obviously this is incorrect.
Which phrases are incorrect here: the names of the procedures or the assisting popup texts? The latter option is most unlikely, as this would probably not have gone unnoticed for so long. I could not check though, as I don't have the sourcecode (and I am not sure I could work it out).
If one follows the texts (assuming the procedure titles are interchanged), it seems to work OK. If one opts for the other possibility (do the opposite of the pop-up texts, as they are associated to the wrong procedure-titles), the Inp Offs Adj I does not work OK.
My questions:
1. Which of these two interpretations is correct?
2. If interpret. 2 is correct (adj I fails) than: will the procedure called "Inp Offs Adj I" work with shorted terminals and with a 15 Ohms resistor // R46 (as advised in an earlier forum thread, in case of failing adjustment)?
PS a similar mixup can be found in the TRIM paragraph at the end of chapter 4 in the "first time setup" document on the website.

Postby snoopy_94 » Thu Feb 06, 2014 12:00 am

By what reasoning do you think it is incorrect?
Do what is requested by the pop-up messages!

Indeed, for "Input Offset I adjustment", it is necessary to compensate the offset of the IU converter itself (U8 + U4C and U4D), without taking into account the offset of the sinus generator, so with an open input (and the selection of R22 for maximum gain, done by the firmware).
For "Input Offset U adjustment" it is necessary to compensate the offset of the followers U4A and U4B, so with their inputs connected together.
Caution, the hardware change described in the issue of November 2013 (US edition) must be used with new programs and firmware V 3.0.0 .

PS a similar mixup can be found in the TRIM paragraph at the end of chapter 4 in the "first time setup" document on the website.
I see no such thing. Can you explain?

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Joined: Thu Jan 02, 2014 10:48 am

Postby Guest » Sun Feb 09, 2014 12:00 am

Thanks for reacting Jean Jaques,
I will try to be more precize:

1. In the article about the modifications to V3.0.0 (Dutch version, nov 2013) under "new software [3]", the last sentance reads (in English): ".....Input_offset_I adjustment is performed with shorted input and Input offset U adjustment is performed with open terminals. In my post I described as accurate as I could, how these are interchanged in the software. Your reply tells me, only the titles are interchanged (first of the two possible interpretations), as it leads to a correct adjustment (only in a different order).
2. In the PS I referred to the second last paragraph of "First time setup" Chapter 4. The paragraph mentions first, that the TRIM tests are performed in the order: "open circuit and then short circuit", but just before the text "Remove jumper from J1" it mentions that first the flashing red 'Short-circuit Trim' warning disappeas and later, after the bold "...Jumper J1" the flashing red Open-circuit Trim warning disappeares. As you see, they are interchanged.
Now, these are not serious flaws, but just a bit confusing.
I must add, I am very enthousiastic about your design. I hope I will ever solve my remaining problem, as mentioned in my other recent thread.

Postby snoopy_94 » Mon Feb 10, 2014 12:00 am

1. It seems that there was an error in the French to German translation!
The French text is:
Nouveaux programmes [4]
... AU2011 qui passe lui aussi en version 3.0.0 : au menu initial Réglage input_offset... se substituent deux menus Réglage input_offset_U... et Réglage input_offset_I..., le premier avec un court-circuit à l’entrée, le second avec un circuit ouvert.
It is very important that various offset compensation are carried out successfully.
2. Order is not important, but you are right, there is possible confusion.
As the jumper J1 is already in place, clicking the TRIM button launches the TRIM compensation operation in short-circuit... and after removing the J1 jumper, the same compensation operation in open-circuit.

Posts: 90
Joined: Thu Jan 02, 2014 10:48 am

Postby Guest » Tue Feb 11, 2014 12:00 am

Thanks JJ for clarifying this. This thread can be closed.
Just to prevent any misunderstanding: I do not know about the contents of the German issue; I only read the Dutch, so that is where the error has been noticed (I checked again).

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