outside control voltage signal precesion

[scscsc]

outside control voltage signal precision

Hi, everybody,
I have a voltage controlled block in my chip. the control voltage will be generated by a outside device, and tuned manually during chip test. Does anyone know the precision that the outside voltage control signal can achieve normally? thx in advance

 

[kripacharya]

thats interesting. You want manual control, but to very high precision ? Its hard to say what precision if its manual... like maybe a multiturn potentiometer ?

You can get multiturns of 12. One quarter turn is quite achievable manually. Maybe with +/- 10% accuracy.

So that gives you 12 x 4 = 1/48 th of the voltage across the pot per quarter turn
Lets say your total range is 5v. So 1/48th turn ~ 0.1042 volts per quarter turn.
And a +/- 10% on this would make it ~ +/- 10mV accuracy.

Good enough for your app ?

If not, you can get multiturns of upto 25, maybe more. Then your precision would be ~ 5mV

Of course by this time the actual linearity accuracy of the preset will start having an effect, so the calculation gets harder.

 

[scscsc]

thanks for your reply kripacharya, i found a description of a device in the website of Agilent. Can we say that if we use the Low-range volts, amps 25W mode of this power suply, we can generate any voltage between 0 to 7V with an accuracy of 0.016% + 1.5 mV?

6625A Precision System Power Supply, 25W or 50W, 2 outputs
Output Ratings (1 output each)

Low-range volts, amps 25W: 0 to 7 V, 0 to 15 mA
Low-range volts, amps 50W: 0 to 16 V, 0 to 200 mA
High range volts, amps 25W: 0 to 50 V, 0 to 500 mA
High range volts, amps 50W: 0 to 50 V, 0 to 1 A or, 0 to 16 V, 0 to 2 A

Programming Accuracy at 25°C ±5°C (1 output each)

Voltage 25W: 0.016% + 1.5 mV (low), 10 mV (high)
Voltage 50W: 0.016% + 53 mV (low), 10 mV (high)
Current 25W: 0.04% + 15 µA (low), 100 µA (high)
Current 50W: 0.04% + 185 µA (low), 500 µA (high)

Ripple & Noise (20 Hz to 20 MHz) 1 output each

Voltage rms: 500 µV
Peak-to-peak: 3 mV
Current rms: 0.1 mA

 

[kripacharya]

Can we say that if we use the Low-range volts, amps 25W mode of this power suply, we can generate any voltage between 0 to 7V with an accuracy of 0.016% + 1.5 mV?

6625A Precision System Power Supply, 25W or 50W, 2 outputs
Low-range volts, amps 25W: 0 to 7 V, 0 to 15 mA

Programming Accuracy at 25°C ±5°C (1 output each)

Voltage 25W: 0.016% + 1.5 mV (low), 10 mV (high)

Ripple & Noise (20 Hz to 20 MHz) 1 output each

Voltage rms: 500 µV
Peak-to-peak: 3 mV

LoL !! yes i suppose you could. Though a bit more expensive than a multiturn i think.

your accuracy of 0.016% implies ~ +/- 1mV at 7V output, and i suppose lesser at lesser voltages.

However I didn't quite understand the Ripple & Noise spec. which seems to be worse than the Accuracy spec.

EDIT:
just had a quick look at the actual Agilent document... where it says accuracy is 0.16% and not 0.016% !!
That means an accuracy of ~ 11mV at max voltage ?

But I still don't get the meaning of the " +1.5mV(low), 10mV (high)" part

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To continue with the potentiometer concept , you can use (one possibility) a combination of these two items to a very high degree of accuracy & reliablity at a comparatively miniscule cost --

GP02-geared-potentiometer
multi-turn pot

 

[scscsc]

LoL !! yes i suppose you could. Though a bit more expensive than a multiturn i think.

your accuracy of 0.016% implies ~ +/- 1mV at 7V output, and i suppose lesser at lesser voltages.

However I didn't quite understand the Ripple & Noise spec. which seems to be worse than the Accuracy spec.

EDIT:
just had a quick look at the actual Agilent document... where it says accuracy is 0.16% and not 0.016% !!
That means an accuracy of ~ 11mV at max voltage ?

But I still don't get the meaning of the " +1.5mV(low), 10mV (high)" part

- - - Updated - - -

To continue with the potentiometer concept , you can use (one possibility) a combination of these two items to a very high degree of accuracy & reliablity at a comparatively miniscule cost --

GP02-geared-potentiometer
multi-turn pot

I think " +1.5mV(low), 10mV (high)" means for the low-range voltage mode 0 to 7 V, the minimum voltage step is 1.5mV, and for high-range voltage mode 0-50V, it is 10mV