# Tag Info

8

Since you have an example of the signal on your scope, the best thing to do is capture the data and transfer it to a PC. Then use a tool like Matlab or Octave to simulate the effect of different filters. You are looking for a filter, just defined in terms of poles (and maybe zeros) that minimizes the noise, without disturbing the desired features of the ...

5

While more elaborate interrupt- or DMA-based code would be necessary to achieve the best performance, relatively minor improvements to your code would improve the situation already. I'd start by transmitting samples in binary instead of in text. This requires slightly more work at the receiving end, but will cut the required UART bandwidth by at least 2-3x ...

4

Auto ranging would typically be handled by adding a PGA (programmable gain amplifier) in front of your A/D converter. In some instances to make maximum utility of the range of your A/D converter you would also add a programmable offset into the PGA as well. The output of the PGA would get clamped via some diodes to the A/D converter reference voltage range. ...

3

If you have a reference voltage of (say) 3V, the range your input will see is: - 3V * 10k/13k = 2.307V (sensor at 3kohms) 3V * 10k/70k = 0.428V (sensor at 60kohms) If you used a 50uA current excitation and a grounded sensor, the range your input will see is: - 50e-6 * 3k = 0.15V (sensor at 3kohms) 50e-6 * 60k = 3.0V (sensor at 60kohms) With a current ...

3

universal protocol that is used by the likes of USB audio Sounds like the USB Audio Class specification. Is this conversion from output of ADC to USB data stream something which we can do, say, with a microcontroller? Some USB microcontrollers - NXP LPC17xx for example - have example code for USB Audio Class available.

2

Do you have a de-coupling capacitor on the motor itself? If not, add a 100 nF ceramic capacitor across the motor terminals, as closely as possible to the actual motor housing. (Worst case, across the connectors to the motor terminals on your board.) Does the motor run only one way? If so, also add a dissipation diode across the motor, with anode towards ...

2

I think the first definition is closer to being correct, but it's not quite right. For an $N$-bit D/A converter, the maximum output voltage is produced when the digital input word is equal to $2^N-1$, which is the unsigned value with all bits equal to 1. So, the maximum output value is $V_{max}=((2^N-1)/2^N) * V_{ref}$. For large values of $N$, the ...

2

A quick and simple option to investigate is to average the ADC values over a given number of measurements, resulting in a simple low pass filter. Best option would be a ring buffer of a certain size in which you push the most recent value at the end and average across all values in it. This method does come with a maximum delay of the ring buffer length ...

1

You could add a 10x and 100x amplified version of the same signal (or multiply some other convenient factor, like 16x and 256x) , and feed that to other analog inputs. The rest is software. Note that those amplifiers must be very accurate, both in gain and in offset, but you might be able to do some trikery by comparing the readings of values in different ...

1

Depending on your voltage levels, you can do these. Voltage divider, where resistors are switched with a multiplexor Variable gain amplifier External A/D with more bits. This is usually the easiest, and produces good results. Look-up these Analog Devices' A/Ds. Many of them have built-in programmable gain amplifiers (PGA). Protection against ...

1

The AD9862 has an input impedance of 200 ohms typical and that is of some interest but not of major importance when it comes to the outside world interfacing. Generally speaking, a chip input impedance of infinity is easier to work with - in this way it can be ignored providing the chip doesn't sit more than a few inches away from the resistor/components ...

1

I would suggest just using a lower reference voltage rather than altering your signal. By using a lower reference voltage, your 1024 discrete points are spread over 0-3V rather than 0-5. In most cases, using the default reference voltage is fine, but sometimes the extra precision is needed. In order to do this, use a voltage divider with Vout=3V or slightly ...

1

While this doesn't directly address your question, it does describe a problem you are going to run into in the near future. Basically, the ATxmega ADCs are pretty much unusable when connected to the xmega's internal 1.0V reference. You get ~16 counts of noise no matter what you do. The general consensus seems to be that if you want to use the ADxmega ...

1

It's probably also worth mentioning that the sprintf call is probably fairly slow and (if it's the only time you use it) pulls in a lot of library code. Even if you want to keep human-readable ascii, you could probably serialize the number a lot faster yourself than sprintf. While you're at it, you could include the semicolon in the string and make only one ...

1

You can measure with a μC the voltage of the battery which directly powers this μC (without a voltage regulator). You need to have a reference voltage, which doesn't change as the battery voltage changes. The idea is either to measure the battery voltage w.r.t voltage reference, or to measure the voltage reference w.r.t battery voltage. Many μCs have a ...

1

You can do this (assuming voltage is a predictable function of remaining life, but that's another issue) as long as there is a fixed voltage reference available in the system somewhere. Some micros have a fixed voltage reference built in, which can usually be read by the internal A/D or applied as the A/D scale. If not, you have to supply some external ...

1

I'm not really sure what "dissolution" means in this context. In your first example, I would think that 312.5 mV is the step size, or resolution, for a one-count change (also called one LSB). A 5-bit converter would have 25 = 32 steps, so the full-scale range would be 312.5 mV × 32 = 10.000 V. In your second example, you seem to be saying that 0.5 V ...

1

Note: standard pH calibration solutions are NIST to +/- 0.01 pH. few standard meters read better than 0.02 pH (might output the 0.01pH number but look in the manual) and if you're using a standard pH sensor probe (glass bulb) there isn't a man alive who will have much faith in anything you claim tighter than 0.02pH without a very massive proof detailing your ...

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