Heck with Vref+. The best way is to just stick it up close to Vcc, and use an op-amp. That's 2 op-amps, 1 for V, 1 for I. So add another 30 to 60 min. to the task list.

People have sent PM voicing interest in the data logger. Yes, data loggers are awesome!     It will work for any input so long as it's within range of the ADC. That includes JT circuits. IOW, connect the JT to a battery or ultracap and you can data log the ultracaps voltage.

A few webpages I used to brush up on parallel ports,

http://www.codeproject.com/KB/vb/PortAccess.aspx

http://www.codeproject.com/KB/cs/Control_e_appliances/1.gif

Warning, massive pdf, 6.26MB,
http://www.fimee.ugto.mx/profesores/dohernandez/documentos/Parallel_Port_Complete_Programming,_Interfacing_and_Using_the_PCs_Parallel_Printer_Port.pdf

http://www.adwiens.com/projects/electronics/10/ADC0808_PPORT_SCH_LG.gif

Another fat pdf,
http://staff.iiu.edu.my/zzulkifli/mctlab2/old_manual.pdf

ADC0809,
http://www.national.com/ds/AD/ADC0808.pdf

Paul

Hi Paul,

It looks pretty much based on your data that supercaps are nonlinear devices.  So I did a search on "supercapacitor nonlinear" and here is what came up:

http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=4592311

<<<
The role of supercapacitors in designing fuel cell powered portable applications
Harfman-Todorovic, M.   Chellappan, M.   Palma, L.   Enjeti, P. 
Dept. of Electr. Eng., Texas A&M Univ., College Station, TX;

Abstract
In this paper, the role of a supercapacitor in the design of fuel cell powered systems is discussed. First, the electric equivalent circuit model of the fuel cell and the supercapacitor is obtained using frequency analysis, which is essential in establishing a design procedure to size the required supercapacitor. It is evident from the nonlinear model of the supercapacitor that the capacitance increases with voltage. Since the fuel cell voltage is inversely proportional to the output power supplied, it is shown that combining fuel cell with supercapacitor is particularly advantageous to guard against load transients as higher energy is stored while supplying lighter loads.
>>>

So there you go, it is exactly like I speculated.

Good luck with your measurements, but the bottom line is that your supercap or ultracap will not give you more out than you put in.  It is easy to get thrown off by nonlinear devices.  Using LEDs to measure power is a classic one.  LEDs are nonlinear devices and are notoriously difficult to measure power with, not to mention the fact that almost no one seems cognizant of the issues related to the persistence of human vision and how that makes it basically impossible to use your eyes to gauge the relative power between flashing LEDs in separate circuits.  Then the Big Daddy of all nonlinear devices is the battery, and comparing start and end voltages is basically meaningless data.

Anyway, I am pretty much done with your thread and good luck.

MileHigh

Quote from: MileHigh on December 01, 2009, 05:58:06 PM
So there you go, it is exactly like I speculated.

Good luck with your measurements, but the bottom line is that your supercap or ultracap will not give you more out than you put in.  It is easy to get thrown off by nonlinear devices.  Using LEDs to measure power is a classic one.  LEDs are nonlinear devices and are notoriously difficult to measure power with, not to mention the fact that almost no one seems cognizant of the issues related to the persistence of human vision and how that makes it basically impossible to use your eyes to gauge the relative power between flashing LEDs in separate circuits.  Then the Big Daddy of all nonlinear devices is the battery, and comparing start and end voltages is basically meaningless data.

MileHigh,

I have already discussed the topic, which is why the last posted data covers a wide voltage range.

What you have posted shows nothing new. To be honest, all you have done is posted information that is so basic that it goes without saying, but yes, I have already posted about this. Nothing new.

Quote from: MileHigh on December 01, 2009, 05:58:06 PMthe bottom line is that your supercap or ultracap will not give you more out than you put in.

I have no idea if the ultracap will show cop>1, we'll find out for certain, no speculations, but sadly enough one fact remains, your statement clearly shows a closed mind.

Quote from: MileHigh on December 01, 2009, 05:58:06 PMAnyway, I am pretty much done with your thread and good luck.

Done? What have you shown here? Anything besides what I've already discussed, and what everyone here already knows?


Paul

and Heres the rest you left out :The other advantages of connecting the supercapacitor in parallel with the fuel cell are shown to be: (a) increased steady state stability when powering constant power loads, (b) voltage and system performance stability during fuel cell dynamics (purging), and (c) increased fuel efficiency (i.e. reduced hydrogen consumption). For transient stability analysis, the effect of fuel cell internal impedance (extra element), along with the impedance of the nonlinear supercapacitor, on the transfer function of the DC/DC converter is analyzed. Finally, experimental evaluation and comparison of fuel consumption in the conventional and hybrid systems is performed, showing that the hybrid source has improved fuel utilization. From these results, it is shown that the proposed approach permits optimization of energy management and improvement of dynamic performance of the power conditioner. The experimental results obtained on 20 W and 30 W PEM fuel cell/boost converter systems demonstrate the validity of the proposed approach.

Ans then again these are ULTRA capacitors and not Super capacitors . There are sizes see . Mini maxi super and Ultra

Hi,

Part of today was spent on getting the ADC input noise lower. It's now as quiet as a church mouse.

The other part of the day was spent on software. Making it a lot fancier. The file log system is being cached in memory and then it periodically dumps the cache into a file. Also keeps a file backup of the ongoing log in case something happens to the main log. The software also shows a plot of both ADC channels like an oscilloscope view. On top of that is channels in text. Above that is a bar that shows how fast it's logging the data. On my Windows XP machine it's doing ~ 800 logs per second. Another addition is an alarm that goes off if the software cannot connect to the ADC. It would be devastating if after 5 hours of logging data and something happens.

Unless another unexpected thing happens, everything should be ready to go tomorrow.

Paul