44
votes
What does the "proportional symbol" (∝) mean when used as a time unit prefix?
In the common ISO 8859-1 encoding, µ is encoded as 0xB5.
In the Windows Symbol typeface, ∝ is encoded as 0xB5.
The Symbol font has been commonly used for Greek letters; µ is the only Greek letter that ...
- 20.1k
17
votes
Accepted
Discharge time of 12 V 8.4 Ah at 5 mA
I have a motorcycle battery rated as 8.4Ah (20HR). It also says 8Ah (10HR) and I am not sure what´s the difference.
The capacity decreases at higher discharge rates. The figures are telling you that ...
- 180k
15
votes
Accepted
Can I use capacitor to measure time?
Yes, this is a well-established method of measuring with resolution in the picoseconds without requiring impossibly high clock frequencies. You switch a current source to a capacitor.
The generic term ...
14
votes
Accepted
Are civilian GPS signals cryptographically signed?
GPS can be spoofed without decrypting or creating signals. Therefore, the system cannot be made secure by cryptographic signatures.
The conceptually simplest way to spoof is to erect a number of ...
- 986
13
votes
STM32F20x ADC sampling time/rate
I'll let you work out the details for your particular case, but I'd like to add some more clarity.
First off, I've opened up an errata report on RM0410 (the reference manual for my chip) here.
I'll be ...
- 1,849
13
votes
Accepted
NPN transistor slow to turn off even when operated outside of saturation region
The main problem is likely to be Miller capacitance (internally 10 pf or so between collector and base) and the 15 kohm base drive resistor. CR time is going to be 150 ns due to that alone and will ...
- 473k
12
votes
Accepted
How does the 4th satellite in GPS know the time offset?
The satellite doesn't know your timing offset. GPS is a one-way street: the satellites basically only transmit their own time. Your receiver needs to do the rest, as the satellites can't know you even ...
- 100k
10
votes
Accepted
Measuring the activation time of a solenoid
I'm wondering if there are other approaches which I haven't thought
of.
Idea:
If you superimpose a small high frequency AC signal on top of the DC that drives the solenoid, you can infer the ...
- 473k
8
votes
Trapezoidal approximation of inductor current from moment to moment
Your calculation of the current increment during one timestep by multiplying the derivative of the current at t=t1 i.e. V(t1)/L with the timestep t2-t1 is known as Euler's integration method. It's ...
- 81
7
votes
Accepted
Why do car blinkers seem to synchronize and then diverse from each other?
Figure 1. Beating of two frequencies. (Illustration by Transistor.)
Any two systems operating at differing frequencies will "beat" at the difference between the two frequencies. So if one ...
- 180k
7
votes
Can I use capacitor to measure time?
Within some very wide tolerances, yes it will work. Capacitors have initial tolerances, measured in %, some types are affected by DC voltage - they change their value based on the applied voltage. All ...
- 7,705
6
votes
Safety of current with duration
Of course and it is disciplined by different standards in different countries. I am used to IEC standards, so IEC 60479-1 is the reference for current-duration limits, distinguishing between ...
- 1,609
6
votes
Accepted
Does the Epson RX8900 real time clock count the year "00" as a leap year?
Despite the misleading series in the datasheet, the RX8900 does consider the year "00" to be a leap year.
I tested this empirically by setting the date to Feb 28th, 00 and letting it roll to see ...
- 10.2k
6
votes
What is a "discrete time controller"?
Continuous time is the world we live in - something can happen at any time, 1 second? 1.1 seconds? 1.111111111111 seconds?. Your plant will exist in real time - e.g. a motor speed would be continously ...
- 70.7k
6
votes
How does the 4th satellite in GPS know the time offset?
Although there are multiple timing offsets in the context of GPS operation with some of these parameters being measured and the others calculated, most probable you are talking about the timing offset ...
- 4,630
6
votes
Reliability of Sampling Rate vs Absolute Timestamps
If the sampling rate of these sensors is reliable enough, I could just record the initial timestamp and the sampling rate and assume uniform sampling
I spent 30 seconds looking at the datasheet (Ctrl-...
- 81.9k
6
votes
Accepted
What does the "proportional symbol" (∝) mean when used as a time unit prefix?
It is most likely an encoding error in the PDF file. It is simply the wrong symbol.
Here's a section of the BT136 datasheet showing the dynamic characteristics:
It shows ∝s for several things, among ...
- 73.6k
5
votes
Whats the difference between an FPGA and an ASIC
How long does it take to build an FPGA?
I'm assuming you mean "fabricate" here, rather than build.
The time to fabricate an FPGA is irrelevant to the user in most cases.
Since they're all fabricated ...
- 134k
5
votes
Calculating R and C for schmitt trigger debouncer
For filtering, C1 should be at the inverter. R2C2 form the debouncing filter. R2 can be a high value so C1 can be smaller. R2C2 also form a low pass filter to remove RF interference and noise spikes.
...
- 5,493
5
votes
What is a "discrete time controller"?
A discrete time controller is any circuit that makes internal state changes (i.e., decisions) at discrete points in time rather than continuously, typically under the control of a periodic clock. This ...
- 178k
5
votes
How are system clock and oscillator frequency related?
yes. A square/rectangle wave is required.
not necessarily. For example a base model 8051 microcontroller divides the oscillator frequency by 12. Thus the counter/timer clock is oscillator/12. Compare ...
- 6,678
5
votes
Analog-to-digital conversion time on MSP430FR6989
Rather than just give an answer detailing exactly which page this is on, or giving the straight answer, this will be more of an answer explaining how to navigate through the datasheet to get to the ...
- 12.2k
5
votes
Can I use capacitor to measure time?
To get a linear voltage change over time, you need to charge the capacitor from a current source and not a voltage source. Then Q = I.T = V.C and the time is simply T = V.C/I.
- 19.5k
4
votes
Accepted
STM32F20x ADC sampling time/rate
That depends on the source of the measured signal. Some time is required to charge the ADC input capacitance, so if your signal circuit can't sink / source enough current the sampling time will need ...
- 2,634
4
votes
Are civilian GPS signals cryptographically signed?
The last generation of Galileo systems use cryptographic authentication of geolocation transmissions, called navigation message authentication or NMA. GPS is also in progress of implementing their own ...
- 141
4
votes
Discharge time of 12 V 8.4 Ah at 5 mA
From here:
If a battery has a rating of 100AH @ 20Hr rate, then that battery
was discharged over 20 hours with a 5 amp load. Starting batteries, on
the other hand, are typically rated at 10Hr ...
- 8,144
4
votes
Are consumer systems able to measure nanosecond timings?
If your question is: is there a way with a low cost product to reliably measure a difference of 6 ns?
Then the answer is yes. There are for example time to digital converters which cost less than 1$ ...
- 18.1k
4
votes
Accepted
How do digital watches steadily increment the internally stored time without fluctuations in speed while running other logic at the same time?
As was commented, your standard digital watch doesn’t have a processor running code. It’s going to have digital logic doing everything in hardware, all in a single custom chip. Economy-of-scale says ...
- 8,374
3
votes
How create a high precision clock in an FPGA?
Your question is rather vague and rambling, and contains what appears to be a few misconceptions, so I'll just offer some broad thoughts here, based on my work in time transfer and synchronization ...
- 178k
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