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20

Your measured short-term stability is about +/-0.01%, which isn't bad for an uncompensated RC timer. You can improve it by using low temperature coefficient resistors and capacitors in the timing circuit, maybe by bypassing pin 5 to ground, by isolating the circuit thermally and electrically, in the extreme controlling the temperature in an oven, powering ...


13

I don't think you will ever get the accuracy and stability you want from a 555 timer. The pulse width is determined by the values of resistors and a capacitor, and the values of these elements will change with temperature and over time. For a precise pulse duration you should be looking at a crystal oscillator with a digital counter to generate the desired ...


5

You misunderstand how a thermocouple works. A thermocouple generates a voltage that is more or less proportional to the difference in temperature between the junctions. If your "hot" junction is at 21C and your "cold" junction is also at 21C, then the difference voltage will be zero. So reading 0V from a thermocouple at thermal equalibrium is exactly ...


5

You need a DC path for the in-amp bias currents, for example you could ground the junction or connect one lead or both to ground through a relatively high value resistor (the thermocouple and leads are usually well under 100 ohms, so any resulting error should be minimal. In order to get predictable filtering you will need to add some series impedance to ...


3

I had a look at your audio file. You have two major noises going on. One is powerline hum. You have a 60 Hz hum, with a lot of harmonics. This is the spectrum: The biggest peak is at 60 Hz, the next highest one is at 180Hz. The other thing you've got going on is a high pitched squeal at around 10kHz, that seems to be mixed with some other trash: The ...


3

The above presented approach would make sense to me if two buffers were used in order to repeat the signal and then divide it on the two 47K resistors. But why use such a configuration, where the non-inverting input is tied to the output? It's a faulty circuit - U3A and U3B should not have positive feedback - I would say that the inputs on both those ...


3

A few suggestions to start: No slots in ground planes that current flows. Grounds connected to single point ground with no loops. Current carrying tracks run above ground plane or directly above ground return tracks. Decoupling caps with minimum inductance path to ground at every IC power pin (ie any pin that is liable to source/sink more than signal ...


1

Is this a correct conclusion? No, for two opposing reasons. In theory, an amplifier can have a noise figure of less than 3dB, because it is not in thermal equilibrium, and the relationship between input impedance and noise only holds for a system in thermal equilibrium. So if you could build an ADC that acted like an amplifier, you could get a very low ...


1

the door is a reflector, if there is electrical noise produced inside the box closing the door will somewhat prevent its escape and increase noise levels inside the box Try fitting ferrite noise suppresors on the power wires running in and the DC wires running out of the power supply, (put both wires through each) alternatively you could add a window in ...


1

Electric Field coupling ABOVE A PLANE is proportional to 1 / distance^3. Electric Fields will happily divert (most of the electric flux) to nearby metal regions, strongly attenuating the remote flux coupling. But the Fields still exploit ALL POSSIBLE paths, thus your remote coupling is never reduced to Zero. That said, large nearby pieces of metal (tied to ...


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