shumifan50
- Jan 16, 2014
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Hi Simmon,
When you have multiple sensors, it is often convenient to have the full-scale range read the same for each. Since we tend to think in decimal, it can be convenient to adjust the output of even a single sensor to some convenient value, such as "10."
That appears to be what the circuit does and instructions describe. The voltage divider, which is made up of a 1 M resistor and 100K pot/decade box allows one to adjust the voltage reading of a reference voltage from the sensor/computer to 10V.
Can you link to the procedure manual? Some important steps may have been lost in the snip you show.
John
When you have multiple sensors, it is often convenient to have the full-scale range read the same for each. Since we tend to think in decimal, it can be convenient to adjust the output of even a single sensor to some convenient value, such as "10."
That appears to be what the circuit does and instructions describe. The voltage divider, which is made up of a 1 M resistor and 100K pot/decade box allows one to adjust the voltage reading of a reference voltage from the sensor/computer to 10V.
Can you link to the procedure manual? Some important steps may have been lost in the snip you show.
John
.
Why do they use a reference voltage?
If they didn't use a reference voltage or this normalizing circuit, what would be different?
Does the 1 meg ohm resistor change the DVM input impedance?
When do you use this normalizing circuit for measurements mostly? for what type or kind of circuits?
You are giving us just a small peek of the procedure from which it is impossible to answer all of your questions.
Let me step back and ask you, if you have a voltmeter, and you want it to read "10" as a full scale value for the maximum voltage from a sensor that produces more than 10V (only for example, you have not given enough information to be sure), how would you go about doing that? Would you not consider getting a voltage that is the same as the maximum sensor output (i.e., "reference"), putting that across a voltage divider, and adjusting that divider so it reads "10" on the voltmeter? Sure, there are other ways to do it, and a simple divider won't work, if the source is less than "10," but your initial question was, basically, what does this voltage divider do. Have you read the manual? Do you now understand the concept of "normalizing?"
And yes, you have put a 1M resistor in parallel with the DVM's input impedance. That will change the impedance the source sees a little, but if the output impedance of the source is only 100 ohms, the effect will be pretty small. That is not always the case and is one reason there are other methods to "normalize" meter readings.
John
Let me step back and ask you, if you have a voltmeter, and you want it to read "10" as a full scale value for the maximum voltage from a sensor that produces more than 10V (only for example, you have not given enough information to be sure), how would you go about doing that? Would you not consider getting a voltage that is the same as the maximum sensor output (i.e., "reference"), putting that across a voltage divider, and adjusting that divider so it reads "10" on the voltmeter? Sure, there are other ways to do it, and a simple divider won't work, if the source is less than "10," but your initial question was, basically, what does this voltage divider do. Have you read the manual? Do you now understand the concept of "normalizing?"
And yes, you have put a 1M resistor in parallel with the DVM's input impedance. That will change the impedance the source sees a little, but if the output impedance of the source is only 100 ohms, the effect will be pretty small. That is not always the case and is one reason there are other methods to "normalize" meter readings.
John
shumifan50
- Jan 16, 2014
- 579
- Joined
- Jan 16, 2014
- Messages
- 579
Have you read the article on the link that I posted - it explains that and many more concepts about instrumentation.
Normalization, standardization, and calibration are terms that refer to measurements and all have something in common. Since we are talking about normalization, let's look at that:
Let's assume you drive a car. Have you ever noticed that the "normal" meter indications for water temperature, oil pressure, and battery charge have the indicator needle vertical? In the USA, where the "normal" speed limit is about 60 mph, the speedometer also is vertical. If you are flying an airplane, the course deviation indicator is vertical when you are lined up on course. North usually points straight up.
If you look at an analog clock, where do the hands point at noon or midnight? Do they point straight up (or down), or do they point to some position off that centerline?
There is no technical reason for any of those normalizations. The normal oil pressure could just as easily be 1/4 way up the scale and the normal temperature could be 3/4 way up the scale, and so forth.
Normalization makes it easy for humans to interpret instrument readings and to react accordingly. If you can't understand the need to do that, maybe someone else here can explain it better.
John
Let's assume you drive a car. Have you ever noticed that the "normal" meter indications for water temperature, oil pressure, and battery charge have the indicator needle vertical? In the USA, where the "normal" speed limit is about 60 mph, the speedometer also is vertical. If you are flying an airplane, the course deviation indicator is vertical when you are lined up on course. North usually points straight up.
If you look at an analog clock, where do the hands point at noon or midnight? Do they point straight up (or down), or do they point to some position off that centerline?
There is no technical reason for any of those normalizations. The normal oil pressure could just as easily be 1/4 way up the scale and the normal temperature could be 3/4 way up the scale, and so forth.
Normalization makes it easy for humans to interpret instrument readings and to react accordingly. If you can't understand the need to do that, maybe someone else here can explain it better.
John
Simmon,
Here are some other examples: http://www.edaboard.com/thread308994.html
It appears to be a popular question.
John
Here are some other examples: http://www.edaboard.com/thread308994.html
It appears to be a popular question.
John
