Scaling Question

mathematical logic translationresults:

GAIN = 0,3375
Offset = - 33,75

so we can set: Gain to 0,34 and Offset to 34
The result is a translation 1 V to 0 Fand 5 V to 136 F

Best regards
Betel

Hello,

the way from Rosa needs, that 0 V input should be the value 0 F, but Controls_Gay want to translate 1 V input to 0 F !!!


For all which want to scale in future analog input values or to carry out calculations with analog values, here an implementation concept:

The corresponding connections between input voltage ai and output Ax of the analog amplifier about the parameters of Gain and Offset is described in chapter 4.3.6 in the handbook. The general equation of the LOGO amplifier's says according to handbook (for the adjustments "0..10V" and "no sensor"):

Ax = Ai * GAIN + OFFSET
validly for Ai in the range of 0 (= 0,00 V) to 1000 (V =10,00), if the input Ai comes from an analoge input pin.
In all other cases Ai can be in the range of - 32767 to 32767.
Ax can be always in the range of - 32767 to 32767.

Now you wanted a conversion of Ai,minimum to Ax,minimum and Ai,maximum to Ax,maximum, so general as follows GAIN and OFFSET can describe are determined:

1.) If Ai,minimum = 0 is valid, GAIN and OFFSET can directly calculated in the dialog box of the characteristics of the amplifier, becaus it is always:

OFFSET = Ax,minimum
and
GAIN = (Ax,maximum - Ax,minimum) / Ai,maximum

2.) Is Ai,minimum not equal to 0, then GAIN and OFFSET as follows can be calculated :

Ai,maximum * Ax,minimum
Ax,maximum - -------------------------------------------
Ai,minimum
OFFSET = ----------------------------------------------------------------------------
1 - (Ai,maximum / Ai,minimum)

and

GAIN = (Ax,minimum - OFFSET) / Ai,minimum


and with values of Controls_Gay:

OFFSET = 135 - ((500 * 0) / 100) / [1 - (500 / 100)] = -33,75 --> -34
and
GAIN = 0 - (-33,75) / 100 = 0,3375 --> 0,34
Now you must fit the values to the range of the LOGO-amplifiver!

With modified values for Gain and offset you can also create problem oriented conversions (that is scaling). The placeholder named "measuring range" (in the dialog box of the characteristics of the amplifier) ar for the limits of the new range of values calculated with Gain and offset (exclusively on the base of entrance values 0 to 1000). The designation "measuring range" is therefore extremely misleading. The using of decimal places for displaying (see notes) must be in this case already included so that also several analog amplifiers behind each other (in series) must be used where appropriate.

Notes:

The analog functions of the LOGO can at entrance values Ai and at output values Ax (= "current values Ax") only work with integer values, so that a roundoff is carried out where appropriate (cf. LOGO handbook). In this case the integervalue x becomes from x,0 to x,4 and from x,5 to x,9 the result is the integer VALUE x+1!!! At the example 5/4=1,25: Ai = 5; GAIN = 0,25; OFFSET = 0 shows a value of Ax = 1!

In order to be able to announce also decimal values now, in the corresponding functions exclusively for the representation in message texts the number of decimal places can be defined (n = 1 to 5). From for example 12345 as current value of an analog amplifier is indicated then therefore with 2 decimal places 123,45. Every decimal place is in this case then a multiplication of the actual value by the factor 1/10 = 0,1 equally significant, something with a concrete "circuit" is to be considered (for example through preceding multiplication by n * 10 by means of n of further in series pre-connected amplifier functions). Simultaneously the absolute range of values of the advertisement keeps on being located so: 32767 --> 327,67 !!! Unfortunately neither the "number of the decimal places" nor the parameter "Gain" (the corresponding analog functions) through a reference to a value of another function can be defined!

Considering this state of affairs makes itself now with values of Ai not too big also to the rounding errors reduce or exclude. At the example with Ai = 5 is let, through regulation of 2 decimal places (in the 2. amplifier for the advertisement) and the use of 2 (or more, because -10,00 < GAIN < 10,00)amplifier functions switched in series with values adjusted on each other for GAIN, to avoid the rounding error (= through multiplication of Ai by 100): GAIN_amplifier1 = 10, GAIN_amplifier2 = 2,5 (Instead of 0,25 and a further pre-connected amplifier with GAIN=10). All further decimal places are always 0 at GAIN = 0,25 and integer Ai [On the other hand at a GAIN of 0,40 an advertisement with 1 decimal place is sufficient (for example 7 * 0,4 = 2,1), all further decimal places are always 0 at GAIN = 0,40 and integer Ai (in particular also the 2nd decimal place that can be renounced therefore in the advertisement and the calculation!).]

During the preselection for the sensor type attention is to be paid to following:

• at the entrances I7 and I8 at the basic module are only possibility "0..10V" and "no sensor" .
• The connection of sensors with current output "0..20mA" and/or "4..20mA" is possible only with the entrances of the analog modules (Standard-analog or PT100-module)
• PT100... is only near the PT100 analog input module possible

The settings "0..10V" and "no sensor" show also identical output values Ax with handicap of identical values for Gain and offset at identical inputs Ai. At "0..10V" the specifications of the "measuring range" are helpful, when a sensor is supposed to be evaluated 0 to 10 V. In this case the signal voltages become 0 to 10 V "translates into the range of values 0 to 1000, if Gain = 1 and offset = 0 (cf. for this purpose handbook)! If using now 2 decimal places (for the advertisement), these values 0 to 1000 displayed as 0,00 to 10,00 are indicated then (what corresponds to the input signals in V). Ergo means every decimal place a division of the bloom output value Ax/10 (only for the advertisement, otherwise knows the LOGO only integers!)

Best regards
Betel