# Experimental Physics and Industrial Control System

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 Subject: Re: aiRecord conversion From: Dirk Zimoch To: Bruno Seiva Martins Cc: tech-talk@aps.anl.gov Date: Tue, 28 Aug 2012 15:12:21 +0200
```Hi Bruno,

```
Many drivers overwrite EOFF and ESLO with their own calculations (from EGUL and EGUF and their own assumptions about the raw value range).
```
So the important missing information is: What driver are you using (DTYP)?

Dirk

Bruno Seiva Martins wrote:
```
```Hi all,

```
I am having trouble trying to adjust the conversion parameters of an analog input record for a A/D converter. My AD accepts voltages ranging from -10 to 10 volts and has a resolution of 12 bits.
```
For -10 volts, it produces a digital output of 0
For 10 volts, 4095

I configured the conversion fields as follows:

EGUF: 10
EGUL: -10
AOFF: 0
ASLO: 1
EOFF: 0
ESLO 0.004884   // which is (EGUF - EGUL) / 4095
ROFF: 0
LINR: LINEAR

```
Those values seem right to me but, for example, RVAL=1005 gets converted to VAL=4.9084, when it should be VAL=-5.0916. The problem seems to be that the conversion formula isn't taking into account the EGUL field.
```
According to the EPICS record reference for aiRecord:

The record processing routine performs the following algorithm for
all records except those that use the |Soft Channel| device support
routine. Be aware that step 3 is performed only when the record
specifies LINEAR:
1. Val= RVAL + ROFF
2. Val = Val * ASLO + AOFF
If the conversion algorithm is |LINEAR|, the raw value is converted
via the equation:
3. val = val * ESLO + EGUL

```
Seems like the step 3 is not being completely executed, or considering EGUL = 0...
```

```
Does anybody know what is wrong? Probably I'm missing something really obvious, but I couldn't figure it out...
```

Bruno Seiva Martins

```
```
```

Replies:
Re: aiRecord conversion Bruno Seiva Martins
References:
aiRecord conversion Bruno Seiva Martins

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