differential amp vs instrumentation amp

[cubdh23]

Can someone please explain to me the difference btw differencial amplifiers and instrumentation amplifiers? Dont they do the same thing?
Also which is better in getting rid of noise in an experiement where 0-5 Volts is moving through about 20 feet of wire?

 

[cubdh23]

Iv already found this out nevermind.
thanks
bye

 

[CoTang]

Might as well tell us so that other people would know.

 

[heathtech]

Brief description/instrument amplifiers and their advantages

If he won't expand on it, I will only mention that instrumentation amplifiers offer very good precision and linearity, which is a requirement in most scientific instruments.
I work with instruments that require calibration on occasion. For anyone who does not know this, it might be of interest, because it is a whole field of electronics in itself: Linearity can be described as the ability of a device to amplify an analog signal at proportional levels. A closely related term for GAIN in an instrumentation amplifier is proportional band. For instance, if a sensor is detecting a phenomenon with a value of 1mV, and the maximum value detectable by the sensor is 10mV, a linear amplifier will increase the signal in a proportional way (ex. increasing from 1mV:10 mV to 10mV:100mV) There is usually a gain adjustment associated with these type of amplifier circuits, as well as a bias or zero adjustment. In this types of circuits, a dual point calibration might be performed with a known reference standard. For instance, if the sensor is a temperature probe, and the range of temperature of interest is 0-100 degrees, the probe would be inserted into a calibration bath controlled at 100 degrees and verified with an ASTM certified mercury thermometer. A voltmeter might be observed to see if the amplifier gain at this point is indeed 100mV. If not, the gain adjustment would be tweaked to correct any bias. The probe would then be put into a bucket of ice-water, which ice water at the melting point has the characteristic of maintaining 0 degrees until fully melted. The amplifier output would be observed for a reading of 10 mV. (BTW, the reason 0 volts is seldom used for a bottom scale value is because we can't be certain that the amplifier would begin to react at the appropriate starting point. In other words, an increase of .5 at the sensor might be slightly below the threshhold of the amplifier, and would go undetected. So, instruments are best adjusted to have a voltage level represent bottom scale or zero.) Anyway, a zero point adjustment would be made with the other trimmer pot, to correct bottom scale bias. These two proceedures might need to be performed more than once at top and bottom scale, because they usually interact with each other. Once the sensor is calibrated to the amplifier, it should be very LINEAR in it's amplification. A good way to verify this would be to check it at midpoint, 50 degrees. It should reflect a good linear and precise signal at all points throughout the range. Again, this is the important characteristic of instrumentation amplifiers, where as differential amplifiers might not reflect the same precision.

 

[Jay.slovak]

Re: Brief description/instrument amplifiers and their advant

heathtech, did you notice you have the same Avatar as williB ?

 

[heathtech]

Yes, I did notice this, should I change it? I got it from the selection here on the forum, and I like it because it lets people know what country I am in.
Anyway, I hope my post about instrumentation amplifiers is informative. I have also considered writing a string about tuning PID controllers (proportional, integral, and derivative) and the concept of quarterwave-amplitude-dampening. I could almost write a book about that.

 

[Jay.slovak]

Yes, I did notice this, should I change it? I got it from the selection here on the forum, and I like it because it lets people know what country I am in.
Anyway, I hope my post about instrumentation amplifiers is informative. I have also considered writing a string about tuning PID controllers (proportional, integral, and derivative) and the concept of quarterwave-amplitude-dampening. I could almost write a book about that.

Yes, your post is very Informative, write more Teoretical Posts and Form them into Sticky. That's usefull.

I have nothing against your Avatar, it's just my Graphical memory is better than text memory, so I try to remember people by looking at their Avatar, and for second I though you are williB :lol:

 

[heathtech]

cool,

well, just for fun, I modified my av a little to set me apart. thanks for pointing that out, Jay.

 

[Jay.slovak]

cool,

well, just for fun, I modified my av a little to set me apart. thanks for pointing that out, Jay.

Yay, nice