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| Community Bench Meter |
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| jahonen:
BTW, just checked local Farnell price for STM32F103C6T6 (72 MHz ARM Cortex-M3, 32 kB flash, 10 kB RAM), 4,27€/each. Compare that to 18F-series PICs, which tend to be more expensive, although just 8 bits. I have programmed PICs using assembly, ARM7s and MSP430s with C. I think that the initial difficulty of the ARM is usually just getting things up and running (like configuring the PLL etc). After you figure that out, ARM tends to be much easier. But much of that can be avoided if you bother to spend more than 15 minutes to read the MCU user manual (and that errata Dave mentioned) :) I guess that one would like to use floating point arithmetic for the calibration calculations and result processing to utilize the ADC resolution optimally. 32 bit ARM is much more suitable to that task. I'm not saying at all that is not possible with 8-bits and with fixed point arithmetic. I have seen so many times at work that it is better to initially choose somewhat overkill chip to do the stuff, since price of the hardware tends to come down with the time, but the complexity of the software tends to go up :) Customers not realizing that will often find themselves doing re-design in panic at the very near the deadline, when it turns out that software has grown much beyond initial expectations :) Regards, Janne |
| charliex:
I wish ethernet was in use a lot more on a lot of equipment, its so much better. There are so many stacks and solutions available as well now. |
| EEVblog:
--- Quote from: Mastro Gippo on January 27, 2010, 03:58:56 pm ---Usb and ethernet cables on a multimeter are just a disaster waiting to happen. It's not a good idea to connect a multimeter to the common ground, because if you don't isolate everything you will end up shorting things to ground if you measure a signal with a floating reference. I think wireless (bluetooth, zigbee, custom 2.4ghz) is a better option. I don't see any benefit in using an ARM, I think all the tasks we need can be easily handled by an easier micro. I suggested the microSD because they're, well, micro, but a regular slot will be ok too because you can find adapters everywhere. Sorry Dave, but I think that a rechargeable battery is a must if we want an OLED diaplay, wireless, SD slot.... But I wouldn't go the SLA route, li-ion are cheap and easy to work with, SLA weigh a lot and has Peukert and is big... We should try to focus on building a meter, and keeping it simple and useful (and CHEAP!!); I understand the enthusiasm, but adding tons of features that don't belong to a meter will only be frustrating in the end imho. :) --- End quote --- Frustrating like rechargeable batteries! You can easily have an a low power dot matrix LCD display with a nice backlight, best of both worlds. And even with the backlight on you could still shoot for 1000 hours operation off D cells. The Newhaven LCD display on my new uWatch design for example takes under 200uA, and backlight works well at under 10mA. OLED would likely not allow long term data logging with continuous display. A agree with SD over micro, much less fiddly and more readily available. No built in direct connect PC comms (Ethernet or USB), it needs to be external and isolated. So some form of clip-on box with a serial IR interface. Dave. |
| badSCR:
Anything hard-wire to computer scars me, about the Isolation problems $$$. *Serial IR ; slower speed, but the SD-Card could be used as a buffer. *An SD-Card or usb flash drive is a must for data logging. (for high speed data logging maybe 1~2Gb RAM) *Auto Ranging? *3~5 channel Volt meter/logic And Dual channel Amp meter. *Would like the ability for 10~20 DC amps continuous. *Ability to measure Resistance, Diodes, Inductors, and Capacitors. *maybe a Transistor tester. *micro volts/amps *maximum 600 Volts to 1Kv ? *phase angle (for three phase power) ? *able to use Fluke Clamp-on Current Probes (for three phase power) ? *low frequency Oscope ability (less then 200Khz) ? *A Wall-adapter for a PSU. *Able to use a Lithium-Ion battery pack from a cordless tool (non-charging). If your some where and the battery dies then you could use the one from a power tool. *D cells or the Big 6volt battery, both are easy to find. *In Resistance mode it could tell you the color code and if it is within tolerance. *Maybe a Composite video output. |
| badSCR:
Could do the Ethernet and use a Wifi Bridge to connect to a PC. And use a buffer. |
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