You might spend more time fetching a car clock from the scrapyard than
if you just sat there with a watch and an ammeter. The mfgr
recommendation is probably to protect you from the surge at start up,
which might surprise you, if you expect say 10 amp draw, but have a one
second surge of 30 amps.

After noting a single cycle of start, run, stop, you then have the
onerous task of sitting beside the fridge all day with a beer or two,
counting, averaging the cycles per hour.

From a warm case of beer start, to keep score, or for all day, opening
the door for 20 seconds, closing it every hour, to work up a "typical"
duty cycle.

Alternatively, charge the battery check the specific gravity, let it
run for say 12 hours, then measure the sg of the battery, and
interpolate the number of amp hours from your battery specs.

How critical is all of this?

Your time is say, 10 bucks an hour. The test equipment to do this
properly starts out ridiculously expensive, then proceeds toward the
incredulous, depending on the degree of accuracy desired.

A laptop data port, some software, an interface, or multimeter with
data output would do for centibucks what you could accomplish by rule
of thumb for a little effort.

Actually, I wonder if a digital audio recorder like windat might record
DC voltages across a current shunt in the DC supply. You would need to
test and calibrate the data.

Terry K

AMPowers wrote:
[snip]
Alternatively, one could build their own embedded system using a few ICs
(I would suggest checking out the PIC16 micro-processor line from
www.microchip.com) but this approach presumes some familiarity with
electronics.

my thought too, then you could have it stay in place and give you
readings from now until whenever. there are a number of really good
hall effects sensors for measuring current that are easy to interface
to a pic processor's a/d. but then of course you've got a "new"
problem of needing to find a way to measure current/voltage so that you
can calibrate the pic and it's sensor ... which is the same problem you
started with haha.

maybe the OP could borrow a data logger or multimeter/laptop setup ...
that's what most people do when they need an expensive tool, borrow it,
or rent it

On Mon, 08 May 2006 21:06:43 -0400, Glenn Ashmore wrote:

They are fairly inexpensive data loggers but probably overkill unless you
are a compulsive tester/experimenter like me. So far I have only used it to
document tests of ice chests (the $60 Coleman Xtreme beat the heck out of
the $150 Iceytek and equaled the $400 Frigid Rigid) but once I start tuning
Rutu it will come in real handy.

I hope you'll publish what you find!

Matt O.

purple_stars wrote:
[snip]
maybe the OP could borrow a data logger or multimeter/laptop setup ...
that's what most people do when they need an expensive tool, borrow it,
or rent it

actually i just looked around and radio shack has a multimeter that can
handle 10amps that has a serial interface on it, even comes with pc
software. costs 70$us, i think i'm going to go get one for myself and
try it out haha

Actually Practical sailor beat me to it. They used a much simpler melt test
but their results were the same as mine. Just shows you can do the same
thing with $10 worth of ice as I did with $10 worth of ice AND $150 worth of
electronics. :-)

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"Matt O'Toole" wrote in message
news
On Mon, 08 May 2006 21:06:43 -0400, Glenn Ashmore wrote:

They are fairly inexpensive data loggers but probably overkill unless you
are a compulsive tester/experimenter like me. So far I have only used it
to
document tests of ice chests (the $60 Coleman Xtreme beat the heck out of
the $150 Iceytek and equaled the $400 Frigid Rigid) but once I start
tuning
Rutu it will come in real handy.

I hope you'll publish what you find!

Matt O.

"Terry K" wrote

After noting a single cycle of start, run, stop, you then have the
onerous task of sitting beside the fridge all day with a beer or two,
counting, averaging the cycles per hour.

From a warm case of beer start, to keep score, or for all day, opening
the door for 20 seconds, closing it every hour, to work up a "typical"
duty cycle.

Alternatively, charge the battery check the specific gravity, let it
run for say 12 hours, then measure the sg of the battery, and
interpolate the number of amp hours from your battery specs.

How critical is all of this?

It's not too critical - Just want to decide whether or not additional
(difficult to add) insulation is warranted.

I don't really need a typical duty cycle - just let the unit run with box
closed for say 12-24 hours, then add temporary insulation and let it run
again. If the external temperature changes this could upset the results. So
need to do test when weather is stable for a few days. I could measure
temperatures, acid SG and battery voltage at intervals.

I think this may give me an idea of whether or not to add the extra
insulation.

Thanks for suggestions!

GBM






Your time is say, 10 bucks an hour. The test equipment to do this
properly starts out ridiculously expensive, then proceeds toward the
incredulous, depending on the degree of accuracy desired.

A laptop data port, some software, an interface, or multimeter with
data output would do for centibucks what you could accomplish by rule
of thumb for a little effort.

Actually, I wonder if a digital audio recorder like windat might record
DC voltages across a current shunt in the DC supply. You would need to
test and calibrate the data.

Terry K

purple_stars wrote:
purple_stars wrote:
[snip]
maybe the OP could borrow a data logger or multimeter/laptop setup ...
that's what most people do when they need an expensive tool, borrow it,
or rent it

actually i just looked around and radio shack has a multimeter that can
handle 10amps that has a serial interface on it, even comes with pc
software. costs 70$us, i think i'm going to go get one for myself and
try it out haha

i purchased one of these meters (46-range digital multimeter part
number 22-812) from radio shack earlier this evening, it's pretty nice.
it has all the usual things on it and includes a serial port so that
you can hook it up to your computer. there is some software that comes
with it for the PC but i didn't install it so i don't really know what
it does, i think it does have data logger functions in it. i wanted to
use the meter's output under linux so i had to write some code to parse
the weird binary data coming out of the meter into something
understandable. anyway, since it took over and hour to write a parser
for the data i thought i would post the code and maybe save someone
else the trouble. it should be trivial to write a data logger based on
this.

----
#include stdio.h
#include stdlib.h
#include fcntl.h
#include string.h
#include termios.h
/**
simple scrap of code for 22-812 46-range digital multimeter from
radio shack that compiles on fedora .. listens to the serial port
at 4800 baud and converts all the weird bits the meter sends
across the line into something human readable, hopefully gives
some poor ******* (you) the chance to watch television re-runs
instead of having to figure out what the bit pattern was, like i
had to. i could have cleaned the code up a lot and cut down on
the amount of code but i left it fat and ugly so you could figure
it out with ease and use it for whatever you want. hardly any
error checking in it. cheers.

LEGAL: public domain, no warranties expressed or implied. if it
burns your house down that's your own fault, you should
have been out sailing anyway. enjoy.
**/
char *mode_str [] = { /** string descriptions of modes **/
"DC V ", /* 0x00 */
"AC V ", /* 0x01 */
"DC uA ", /* 0x02 */
"DC mA ", /* 0x03 */
"DC A ", /* 0x04 */
"AC uA ", /* 0x05 */
"AC mA ", /* 0x06 */
"AC A ", /* 0x07 */
"OHM ", /* 0x08 */
"CAP ", /* 0x09 */
"HZ ", /* 0x0a */
"NET HZ ", /* 0x0b */
"AMP HZ ", /* 0x0c */
"DUTY ", /* 0x0d */
"NET DUTY ", /* 0x0e */
"AMP DUTY ", /* 0x0f */
"WIDTH ", /* 0x10 */
"NET WIDTH ", /* 0x11 */
"AMP WIDTH ", /* 0x12 */
"DIODE ", /* 0x13 */
"CONT ", /* 0x14 */
"hFE ", /* 0x15 */
"LOGIC ", /* 0x16 */
"dBm ", /* 0x17 */
"UNKNOWN ", /* 0x18 */
"TEMP " /* 0x19 */
};
#define VAL_1 0 /* array ptrs for digit positions on lcd screen */
#define VAL_2 1
#define VAL_3 2
#define VAL_4 3
typedef struct {
unsigned char match; /* bits to match */
unsigned char value; /* value if matched */
} bit_patterns;
#define MAX_PAT 18
#define CHAR_BLANK 0x10
#define CHAR_MINUS 0x20
#define CHAR_C 0x30
#define CHAR_F 0x40
#define CHAR_P 0x50
#define CHAR_E 0x60
#define CHAR_N 0x70
#define CHAR_L 0x80
bit_patterns pats[] = {
{ 0xd7, 0 }, /* 0 */
{ 0x50, 1 }, /* 1 */
{ 0xb5, 2 }, /* 2 */
{ 0xf1, 3 }, /* 3 */
{ 0x72, 4 }, /* 4 */
{ 0xe3, 5 }, /* 5 */
{ 0xe7, 6 }, /* 6 */
{ 0x51, 7 }, /* 7 */
{ 0xf7, 8 }, /* 8 */
{ 0xf3, 9 }, /* 9 */
{ 0x00,CHAR_BLANK }, /* (special, blank character) */
{ 0x87,CHAR_C }, /* C (special) */
{ 0x27,CHAR_F }, /* F (special) */
{ 0x64,CHAR_P }, /* P (special) */
{ 0xa7,CHAR_E }, /* E (special) */
{ 0x37,CHAR_N }, /* N (special) */
{ 0x86,CHAR_L }, /* L (special) */
{ 0x20,CHAR_MINUS } /* - (special, minus sign or dash) */
};
unsigned char vals[4];
int make_value()
/**
ok, basically this is the deal. there are 4 bytes (out of 9) that
come out of the serial line that are stored in vals[] and each bit
in those bytes is one of the lcd elements ... yes, that is to say
that for instance the character "8" is made up of 7 different
lcd segments, four vert ones and 3 horizonal. we have to match
those bits against what we have in pats[] in order to get a
real value back that is useful. then we print that and the
various decimal points out. you would probably want to make and
return a string or something and use it somewhere else
**/
{
int val;
int n;
int i;
for(n = (int)0;n 4;n++)
{
for(val = (int)-1,i = (int)0;i MAX_PAT;i++)
{
if(pats[i].match == (vals[n] & 0xf7))
val = pats[i].value;
}
if((vals[n] & 0x08) == 0x08)
printf(".");
switch(val) {
case((int)-1):
printf("[BAD(%02x)]",vals[n]&0xf7);
break;
case(0): case(1): case(2): case(3): case(4):
case(5): case(6): case(7): case(8): case(9):
printf("%d",val);
break;
case(CHAR_C): printf("C"); break;
case(CHAR_F): printf("F"); break;
case(CHAR_P): printf("P"); break;
case(CHAR_E): printf("E"); break;
case(CHAR_L): printf("L"); break;
case(CHAR_N): printf("N"); break;
case(CHAR_BLANK): printf(" "); break;
case(CHAR_MINUS): printf("-"); break;
default: break;
}
}
return((int)0);
}
int main(int argc, char **argv)
/**
main()
**/
{
int i;
int s;
int bit;
int len;
unsigned char c;
int neg;
struct termios newtio, oldtio;
/** set the serial port up for 4800 baud, 8n1 /dev/ttyS0 **/
if((s = open("/dev/ttyS0",O_RDWR | O_NOCTTY | O_NONBLOCK)) (int)0)
{ fprintf(stderr,"open(): (int)0\n"); exit((int)-1); }
tcgetattr(s,&oldtio);
bzero(&newtio, sizeof(newtio));
newtio.c_cflag = B4800 | CS8 | CLOCAL | CREAD;
newtio.c_iflag = IGNPAR;
newtio.c_oflag = 0;
newtio.c_lflag = 0;
tcflush(s,TCIFLUSH);
tcsetattr(s,TCSANOW,&newtio);
fcntl(s,F_SETFL,FASYNC);
bit = (int)0;
/** start reading from the serial port and processing whatever bits
we get from the multimeter. we do this strictly by position,
each "packet" that comes out of the meter is has 9 bytes of
data associated with it, and we just process them in order **/
for(neg = (int)0,len = (int)0;
(i = read(s,&c,1)) = (int)0;usleep(200))
if(i (int)0)
{
switch(bit) {
case(0): /* byte 1 from meter says what the mode is */
printf("[MODE] %s ",mode_str[c&0xff]);
bit = (int)1;
break;
case(1): /* byte 2 from meter contains bits that represent
the actual icons on the lcd screen like the
"OHM" or "HZ" symbols */
printf("[LCD] "); /** print the symbols from LCD **/
if(c & 0x80) printf("Hz ");
if(c & 0x40) printf("OHM ");
if(c & 0x20) printf("K ");
if(c & 0x10) printf("M ");
if(c & 0x08) printf("F ");
if(c & 0x04) printf("A ");
if(c & 0x02) printf("V ");
if(c & 0x01) printf("m ");
bit = (int)2;
break;
case(2): /* byte 3 from meter is more lcd symbols */
if(c & 0x80) printf("u ");
if(c & 0x40) printf("n ");
if(c & 0x20) printf("dBm ");
if(c & 0x10) printf("S ");
if(c & 0x08) printf("% ");
if(c & 0x04) printf("hFE ");
if(c & 0x02) printf("REL ");
if(c & 0x01) printf("MIN ");
bit = (int)3;
break;
case(3): /* byte 4 from meter is one of our lcd values. the
lcd has four actual digits on it, these are what
you are going to be most interested in. each
byte of data has seven "segments" which are the
actual lcd segments which make up the digit, and
another bit for decimal on or off */
vals[VAL_4] = c&0xff;
bit = (int)4;
break;
case(4): /* byte 5 from meter, another digit and decimal */
vals[VAL_3] = c&0xff;
bit = (int)5;
break;
case(5): /* byte 6 from meter, another digit and decimal */
vals[VAL_2] = c&0xff;
bit = (int)6;
break;
case(6): /* byte 7 from meter, another digit and decimal */
vals[VAL_1] = c&0xff;
bit = (int)7;
break;
case(7): /* byte 8 from meter, more lcd symbols */
if(c & 0x80) printf("BEEP ");
if(c & 0x40) printf("DIODE ");
if(c & 0x20) printf("BAT ");
if(c & 0x10) printf("HOLD ");
if(c & 0x08)
{
neg = (int)-1;
printf("- ");
}
if(c & 0x04) printf("~ ");
if(c & 0x02) printf("RS232 ");
if(c & 0x01) printf("AUTO ");
bit = (int)8;
break;
case(8): /* byte 9 from meter, checksum, ignored in this
code but you'd probably want to actually use
it for error checking in your own code */
printf("[CHKSUM] %02x ",c&0xff);
printf("[VAL] ");
make_value(); /* process the digits and make something
out of them. they are stored in the
global variable vals[], 4 bytes worth,
so go parse it and print it out in human
readable form */
printf("\n");
bit = (int)0; /* get the first char all over again */
neg = (int)0; /* reset global negative bit */
break;
default: break;
}
fflush(stdout);
}
tcsetattr(s,TCSANOW,&oldtio);
close(s);
exit((int)0);
}

If the system is based on a Danfoss compressor with an electrical unit older
than about 12 months and doesn't have a "smart" controller like Fridoboat
SSC or Isotherm ASU it will run at a constant speed and use a constant
current so you only need total run time to calculate the relative power
usage. With the new Danfoss AEO electronics or a smart control the speed
varies and you do have to measure the current draw over time.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"GBM" wrote in message
...

"Terry K" wrote

After noting a single cycle of start, run, stop, you then have the
onerous task of sitting beside the fridge all day with a beer or two,
counting, averaging the cycles per hour.

From a warm case of beer start, to keep score, or for all day, opening
the door for 20 seconds, closing it every hour, to work up a "typical"
duty cycle.

Alternatively, charge the battery check the specific gravity, let it
run for say 12 hours, then measure the sg of the battery, and
interpolate the number of amp hours from your battery specs.

How critical is all of this?

It's not too critical - Just want to decide whether or not additional
(difficult to add) insulation is warranted.

I don't really need a typical duty cycle - just let the unit run with box
closed for say 12-24 hours, then add temporary insulation and let it run
again. If the external temperature changes this could upset the results.
So
need to do test when weather is stable for a few days. I could measure
temperatures, acid SG and battery voltage at intervals.

I think this may give me an idea of whether or not to add the extra
insulation.

Thanks for suggestions!

GBM






Your time is say, 10 bucks an hour. The test equipment to do this
properly starts out ridiculously expensive, then proceeds toward the
incredulous, depending on the degree of accuracy desired.

A laptop data port, some software, an interface, or multimeter with
data output would do for centibucks what you could accomplish by rule
of thumb for a little effort.

Actually, I wonder if a digital audio recorder like windat might record
DC voltages across a current shunt in the DC supply. You would need to
test and calibrate the data.

Terry K