Re: [time-nuts] question for expert time guys
Yes, we would need to address that as best we can. I thought of using two different frequencies to combat that to provide additional data. There is also the aspect that the mobile device is not expected to move too fast so if we see a big change we look at it with suspicion. Most likely one distance would be way off from the other two. The accuracy of 3 feet over 150 or 200 feet too should also allow for some error. But I'm not the expert here. Rick On Mon, Feb 4, 2013 at 11:35 AM, James Peroulas ja...@peroulas.com wrote: About this subject, are you concerned with multipath? The signal from two of the basestations might arrive over a line-of-sight path whereas for the third basestation the signal might bounce around before arriving... JP - To time experts/EE's. I would like to triangulate a position of a device which moves using 3 fixed positions devices of known location. The idea is to have these operate on 915mhz or 434mhz or 2.4ghz or appropriate frequency. These two type of devices (fixed and mobile) are all under my control and thus customized as needed. The mobile device (not a phone, custom device) would be the least expensive item. I'd like a range of 150 feet or better and accuracy of 3 feet or better. When manufactured these items they can be calibrated in order to adjust for any variation in IC's, discrete components etc... We can assume for now the temperature is constant 70 degree temperature. Cost is the key design factor. The general flow is: 1. base station 1 indicates we are determining position of device A. 2. Each base station 1, 2, 3 take turns pinging the device to determine distance. 3. A ping consists of (something like, e.g. frequencies as examples) -send 915mhz signal from base station to device -device response ASAP on different frequency -station waits and counts 'time' for return -this is repeated N? times to get best avg/accuracy. -The mobile device does not move very fast 4. Since delays of the process on each unit is calibrated the device and base station would subtrack that time out from the results. 5. obviously with 3 distances we can determine the 2D position of the mobile device I know the time accuracy is the key to count time = feet, 1ns. This overall project is not new concept. How to make it inexpensive is key. how inexpensive, very ;-) no OCXO or expensive components like that. That's my goal, and I'm looking for help on the design/thought process of getting there. I am open to a consulting arrangement for a fee, please email if you like. I've worked with 'regular' EE's (I'm a software guy) but this time accuracy is too much for them. Esp. finding a way to do it inexpensively. Thanks for any thoughts. -- Integrity is a binary state - either you have it or you don’t. - John Doerr ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] question for expert time guys
To time experts/EE's. I would like to triangulate a position of a device which moves using 3 fixed positions devices of known location. The idea is to have these operate on 915mhz or 434mhz or 2.4ghz or appropriate frequency. These two type of devices (fixed and mobile) are all under my control and thus customized as needed. The mobile device (not a phone, custom device) would be the least expensive item. I'd like a range of 150 feet or better and accuracy of 3 feet or better. When manufactured these items they can be calibrated in order to adjust for any variation in IC's, discrete components etc... We can assume for now the temperature is constant 70 degree temperature. Cost is the key design factor. The general flow is: 1. base station 1 indicates we are determining position of device A. 2. Each base station 1, 2, 3 take turns pinging the device to determine distance. 3. A ping consists of (something like, e.g. frequencies as examples) -send 915mhz signal from base station to device -device response ASAP on different frequency -station waits and counts 'time' for return -this is repeated N? times to get best avg/accuracy. -The mobile device does not move very fast 4. Since delays of the process on each unit is calibrated the device and base station would subtrack that time out from the results. 5. obviously with 3 distances we can determine the 2D position of the mobile device I know the time accuracy is the key to count time = feet, 1ns. This overall project is not new concept. How to make it inexpensive is key. how inexpensive, very ;-) no OCXO or expensive components like that. That's my goal, and I'm looking for help on the design/thought process of getting there. I am open to a consulting arrangement for a fee, please email if you like. I've worked with 'regular' EE's (I'm a software guy) but this time accuracy is too much for them. Esp. finding a way to do it inexpensively. Thanks for any thoughts. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Looking for RTC or some combination of MPU/crystal for 0.1ppm accuracy.
Hi, I need to find a solution for a RTC which provides 0.1 ppm accuracy in the form of a RTC/MPU or some other combination, oscillator etc.. I'm creating some sensors which all need to do timed measurements and need to be at the same time. They can get a time beacon every 10 seconds but then need to accurately perform independently 20x / sec. They cannot communicate with each other and other than the time beacon are unconnected. After a period of time they will send their time-stamped data out. I haven't seen anything other than RTC DS32B35/DS32C35 which perform at ~2ppm. I need an order of magnitude better. An atomic clock would be great, but the cost/size has to be low as these are sensors and it would be overkill. Any ideas? Rick ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] position determination over short distance
All, I'm planning doing some experiments in distance measurement. They don't deal with atomic time directly but with extreme short periods of time. I need to determine the position of a instrument with a 1mm accuracy or less. The instrument is not connected to a mechanical device but is separate independent. The surface which the instrument is positioned on is close to the size of a 11x11 square. I thought of using 1 RF transmitters (not sure of freq) on bottom of the device near the surface. The surface would have RF receivers on 3 or 4 edges/corners to receive the signal. If each of the receivers positions are known and they then send a signal to a central circuit (again known positions) how can I differentiate the time of arrival at the central location? Does anybody know of a circuit/chip or system which would determine the time 'difference'. Obviously this is used to triangulate the position of the instrument. Light travels 1 mm in ~3.3 picoseconds so I would suspect the differentiator would have to have that or better resolution. It could also use some proportional method to extrapolate the position since the surface has a fixed size. Any ideas/thoughts? Thanks in advance. Rick Harold ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
