feustel@netcom.COM (David Feustel) (05/04/91)
Does anyone know of a simple DMM front-end for the HP48sx that permits the measurement of R,L,C,V and I values for electronic components? A device with an IR or wire interface would be real popular with EE's. -- David Feustel, 1930 Curdes Ave, Fort Wayne, IN 46805, (219) 482-9631 EMAIL: netcom.com
asmith@acorn.co.uk (Andy Smith) (05/09/91)
In article <1991May4.133115.11892@netcom.COM> feustel@netcom.COM (David Feustel) writes: >Does anyone know of a simple DMM front-end for the HP48sx that permits >the measurement of R,L,C,V and I values for electronic components? A >device with an IR or wire interface would be real popular with EE's. >-- I don't know of a DMM front end for the 48, but I have been toying with the idea of a logic probe with trace facilities, and after Wlodek showed me a moving sequence of sine waves on his 48, I am also pondering the possibility of a simple 'scope facility. A logic probe should be easy, you only need a digital to serial converter with protection for the serial interface, and a small piece of code that samples and displays the readings. The external circuit could be hidden in the probe. A scope is a little more difficult but should be possible as is a DMM, I will have a play with these as soon as I get a 48... Though I hope someone else beats me to it, as these would be really useful:-) Andy
hoford@redwood.circ.upenn.edu (John Hoford) (05/10/91)
In article <6910@acorn.co.uk> asmith@acorn.co.uk (Andy Smith) writes: >In article <1991May4.133115.11892@netcom.COM> feustel@netcom.COM (David Feustel) writes: > >>Does anyone know of a simple DMM front-end for the HP48sx that permits >>the measurement of R,L,C,V and I values for electronic components? A >>device with an IR or wire interface would be real popular with EE's. >>-- > >I don't know of a DMM front end for the 48, but I have been toying with the >idea of a logic probe with trace facilities, and after Wlodek showed me a >moving sequence of sine waves on his 48, I am also pondering the possibility >of a simple 'scope facility. > The with a probe with trace or a scope is the serial port cannot input is not fast enough to read in the data in real time. At 9600 baud only 9600 bytes can be read a second Using an 8 bit digital to analog converter the max frequency would be or 4.8 kHz. This would be too slow for most applications. A better solution would be a bord that used a slot and had its own memory which it dumped the readings to. The calculator could read the ram and and display the images in real time. Cost would probably be too high for me to buy. John D. Hoford
gingell@aurs01.UUCP (Mike Gingell) (05/13/91)
Following the discussion on using the HP48 as a scope, it would be possible, despite the fact that the RS232 is slow, if you use the same technique as is used in sampling scopes. These are used for examining very high frequency waveforms and rely on the fact that most waveforms examined are periodic. You sample the waveform once every n cycles delaying the sample point slightly each time until you have capture a picture of a complete period. It requires a fast sample and hold, and A/D plus some clever timing logic. Mike Gingell, Alcatel, Raleigh, NC USA (919) 850-6444 UUCP: ...!mcnc!aurgate!aurfs1!gingell Internet: gingell%aurfs1%aurgate@mcnc.org
akcs.jwtrav@hpcvbbs.UUCP (John Wettroth) (05/19/91)
i may have a partial solution. i sell a gadget called the adcm-48 that interfaces with the hp-48 over the ir link and offers 4 8 bit analog inputs, 4 ttl/cmos digital inputs and 4 .5 amp digital outputs. it offers a burst mode which allows reading the a/d 100 times a second for "scope" type applications. it is available from edu-calc now for $199. also a little further up the thread john hoford stated that 9600 baud means 9600 bytes per second, actually that's bits per second. his argument is correct but is high by a factor of 10! (480 samples/second is the nyquist limted bandwidth). check out the adcm-48, there is even a simple scope program included on the disk that comes with the unit. good luck.
feustel@netcom.COM (David Feustel) (05/21/91)
What is the input impedance of the analog inputs? Have you thought about building a 12 bit unit? -- David Feustel, 1930 Curdes Ave, Fort Wayne, IN 46805, (219) 482-9631 EMAIL: feustel@netcom.com or feustel@cvax.ipfw.indiana.edu