Talk:Integrator

Attention: Make sure the sum of your inputs does not exceed the machine unit (±10V), otherwise an overload will occur

I don't think this is correct. An overload occurs when the output exceeds the machine unit. However it should be no problem if the sum of the inputs exceeds the machine unit. — Preceding unsigned comment added by MKoch (talk • contribs)

Well, if the sum of the inputs exceeds the machine unit, the output will also do so, isn't it? You could think of cancellation of overloads (like in a sum with three inputs, two in overload but opposite sign, like +15V-15V+5V = +5V). This is a border case similar to saying +infinity - infinity + 5 = 5, because actually an overload value is typically an illegal value on the computer and the upcoming computation is most likely wrong. --Sven (talk) 13:51, 1 October 2021 (CEST)

No, if the sum if the inputs exceeds the machine unit, that doesn't mean the integrator's output will exceed the machine unit. At least not immediately. Your example with +-infinity isn't applicable, because every signal comes from another output and is always in the -1 to +1 range (or slightly above).--MKoch (talk) 14:04, 1 October 2021 (CEST)

When you connect a -1 signal to the input then the output will ramp from 0 to 1 in 1ms. Overload after 1ms. When you connect two -1 signals to two inputs of the same integrator, then the output will ramp from 0 to 1 in half the time. Overload after 0.5ms.--MKoch (talk) 14:15, 1 October 2021 (CEST)

The integrator has three "1" inputs with 1MOhm resistance and two "10" inputs with 100kOhm resistance. If all inputs are connected to one machine unit (10V), the input current into the summing junction is 23 * 10µA = 230µA. The output of the TL074 can drive about 25mA into the summing junction (via the capacitor), that's means there is a safety factor of more than 100. We could connect many more inputs to the same summing junction and it would still work fine.--MKoch (talk) 22:15, 1 October 2021 (CEST)

Thank you for your input. From my perspective, again, these are border cases, as the computing element which outputs a saturated, or overloaded, signal, also triggers the overload signal on the whole board. That is, a LED will pop up, notifying the user that there is something wrong. I made the analogy to a floating point exception in classical digital IEE754 computing. You can instruct your algorithms to stop on such an exception, or you can deal with NaNs and infinities on a one-per-one basis. Of course one can imagine a code where such values correspond to some special, intended meaning and all this is fine. In a similar spirit, inserting an "overloaded" value into some integrator input might be fine, especially for a short time. However, at the moment, I cannot think of a computing circuit where one wants to integrate overloaded values. Do you have one?

All the best, --Sven (talk) 09:51, 4 October 2021 (CEST)

A simple example is the triangle wave generator. See chapter 5.5 in Bernd's book. If you want 0.2ms rise time per machine unit, then the input of the integrator must be +-5 machine units. The sum of the inputs exceeds the machine unit by a factor 5, but this is not an overload condition. Also it's not an overloaded input, because it's only +-5V connected to the "10" input.--MKoch (talk) 14:34, 4 October 2021 (CEST)

Thank you for this example. This shows that we have a divergent definition of overload. Having an input value 0.5 on a weight-10 input is not an overload for me. Instead, an input value of 1.5 on a weight-10 input is an overload in my language. I guess there is little hope for the original sentence to be fixed without a more elaborate language or definition. That's somehow what we tried to avoid in the last months (making the wiki too complex and too tech- or science-speak), but now that we had such a long discussion, I encourage you to adopt the formulation at the page Integrator in a way that you are fine with it :-) --Sven (talk) 21:16, 5 October 2021 (CEST)

I did remove the whole sentence because the integrator has no limit for the sum of inputs. At least not in any realistic case. However the same sentence is correct for the summer.--MKoch (talk) 07:50, 6 October 2021 (CEST)