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| unit resolution per decade choice |
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| julian1:
Consider an instrument, that outputs some operator controlled parameter (V,I,Ohm,W,Hz etc). Two output resolution choices are available/feasible - either 40k/decade or 50k/decade. For example, a voltage-source/power-supply with a 0-10V output range, could choose either of these control schemes; 0-10V/50k count, gives 0.2mV interval. last digit 0.2,0.4,0.6,0.8, 1 mV 0-10V/40k count, gives 0.25mV interval. last digits 0.25,0.5,0.75,1 mV. The advantage of the first scheme is a (slightly) higher resolution. While the second approach achieves similar resolution, but also permits a precise half fraction/unit (ie. 0.5mV) to be cleanly expressed. Which is preferred? |
| Tomorokoshi:
1. Is the fundamental variable a 16-bit register? 2. Can you explain a little about what "outputs some operator controlled parameter" means? For instance, is this a dial for some setting, where the digital value is then displayed somewhere, or is it a numeric entry field? 3. Can the operator input control actually achieve that resolution such that one increment is controllable? 4. Is there a key system reason for needing access to the 0.5 mV value over the 0.4 mV value? |
| Benta:
I have feeling that this is a user interface issue. Look at how oscilloscope inputs are graduated: 0.1, 0.2, 0.5; 1, 2, 5. |
| julian1:
--- Quote ---I have feeling that this is a user interface issue. Look at how oscilloscope inputs are graduated: 0.1, 0.2, 0.5; 1, 2, 5. --- End quote --- Good example. Those values are definitely the cleanest/most intuitive for an operator. And on a scope they are employed for the trace display interval and input ranging. In my case, the ranging is per decade (eg. 0-1V, 0-10V, 0-100V etc), and I am trying to decide how to slice up the resolution of the least significant digit. Having a half-step 0.5 (like a scope) feels like it could be useful. Or maybe, it's a confusing analogy, that doesn't apply to the least-significant digits? --- Quote ---4. Is there a key system reason for needing access to the 0.5 mV value over the 0.4 mV value? --- End quote --- Not in the strict sense - ie. in a tranceiver, a 500Hz half-step increment is required due to conventions around broadcast frequency But I keep thinking about scenarios where 4 or 5 step increments might be better for charting and graphs. Or sweep resolution. Or binning observational data by set parameter, to average/aggregate. Or charting on a log10 transformed scale. Actually, I suspect it doesn't matter either way. |
| TimFox:
The advantage of 1, 2, 5, 10 ... for oscilloscopes is how the results fit into a fixed-pitch graticule on the screen. AC voltmeters often use 1, 101/2 (labeled "3"), 10 etc. since it fit well into a dB scheme. It depends on your requirement. |
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