LMIII Questions

[saltyseaman]

I bought a LiterMeter III dosing pump second hand. When I got it the pump housing was broken, so I contacted you guys and got a new one (thanks!). It's all up and running, but now that it is I have a few questions. The person I was talking to hasn't returned my last 3 emails, so I figured I would post my questions here with the hopes of getting a reply.

What is the purpose of the RATE setting? My meter appears to run at the same speed when it is running and on RUN and when it is running and on ON. I haven't measured the ouput difference, but whether it is set to 999ml/min or 001ml/min the pump appears to run at the same speed, and it definitely pumps out more than 1ml/min when it is on that setting. Shouldn't it slow down or speed up for those settings? Also, it appears to vibrate quite a bit when it is running and pumping a fluid (not so much when it isn't pumping a fluid). Is that normal? If it isn't, is this a problem you have observed in the past with other pumps and do you have any suggestions to make it stop? Other than this it appears to work quite well!

Thanks!

[SpectraPure]

The RATE is what the pump can really do, in ml/min., given the unique arrangement of the installation.

The calibration routine sets the RATE. Version 1.1 let you change it, but version 1.2 does not.

Changing that number to other than the calibrated number just lies to the computer. When the pump is set to ON, it will move water at that *calibrated* rate, not what *you* set it to.

When the pump is on, it's on. No speed adjustment. In RUN mode, each pump runs for a calculated number of seconds every 9+ minute cycle. 150 doses make a day.

The FLOW is the number of liters dispensed each day.

I am not familiar with pumps "vibrating". They are extremely smooth and quiet. Does the box want to dance around, or are the tubes just slapping about? Our instructions mention securing the tubing to prevent that.


Scott
SpectraPure, Inc.

[saltyseaman]

<a href=showthread.php?s=&postid=10281774#post10281774 target=_blank>Originally posted</a> by SpectraPure
The RATE is what the pump can really do, in ml/min., given the unique arrangement of the installation.

Can you elaborate on that? This has me thinking that there would be different unique situations where the RATE displayed would have a different max rate that one couldn't go past on the display, but I don't feel that is correct.

Just so I understand you correctly, changing the RATE does nothing then? The RATE that the pump *actually* pumps is determined by nothing but the calibration and is stored in the computer, and changing the RATE on the digital display is for show only?

If that's the case then no wonder you stopped allowing the RATE to be changed in version 1.2 ;) . After looking through the book and not being able to find any information about what changing the RATE does, I was quite confused. I was doing the math and trying to set the RATE to match up to the FLOW, making it so that the 150 doses were each 1 minute long (i.e. a RATE of 51 ml/min dosed 150 times a day for one minute each dose would be the 7.65 liters/day that the FLOW is set to).

As far as the vibrating is concerned, it is more of the tubes just slapping around (which I secured, making the slapping not cause a problem), but the box vibrates as well. I wouldn't call it as much of a dance as I would call it a wiggle. It doesn't move from the place it is sitting, it just wiggles a bit. It also clicks continously at a rate of about 4-5 clicks per second when the pump is pumping a liquid.

[SpectraPure]

That's why the book does not mention any of those math gymnastics.

If the pump is set up nearby, the actual flow rate will be different than if the pump is two stories below the tank. The computer needs to know the ability of the pump to know how long to run the pump. If reality is 250 ml/min., and you change that to 100, the computer thinks you have a low-rate pump and will run it proportionally longer. Not good.

If the pump is making a clicking sound, take it apart and see if you can determine what's clicking on the inside. If not, send it back and we'll make it right.

Scott
SpectraPure, Inc.

[saltyseaman]

Ok, lets see if I follow you correctly. I think an example will best illustrate this to me. Let's say that I have the pump pumping at a height of 3 feet. I run the callibration and the computer determines that I am pumping 300 mL/min and sets the RATE displayed on the screen to 300. I then leave the RATE displayed untouched and set the FLOW to 6.00 L/Day. The computer then calculates the time required to pump during each of the 150 doses by calculating ((FLOW/150) / RATE)*60 = (seconds per dose). In this example here is what the computer would calculate: (6 L/day) / (150 doses/day) = (.04 L/dose). Then (.04 L/dose) / (.3 L/min) = (.13333 min/dose). Then (.13333 min/dose) * (60 seconds/min ) = (8 seconds/dose). So the computer determined that the pump should run for 8 seconds 150 times a day in equally spaced intervals to dose a total of 6 liters per day.

Now, if I went in there and manually changed RATE to 600 mL/min and left FLOW unchanged at 6 L/day then the computer would use the RATE value that I changed it to and do the math, resulting in the computer determining that it would need to run the pump for 4 seconds 150 times a day to pump 6 L/day.

Since the dosing pump is now running for 4 sec/dose to match up to my manually set RATE of 600 mL/min, rather than running 8 sec/dose to match up to the calibrated RATE of 300 mL/min (which is the rate that the pump is *actually* pumping), the total FLOW will be halved. So the FLOW reads 6 L/day on the display, but it is actually pumping 3 L/day because I changed the RATE from 300 mL/min to 600 mL/min.

Is that correct?

If this is the case then changing the RATE to a different value than the callibration determined *does* make a difference in the quantity dosed per day, and, again, no wonder you stopped allowing the RATE to be changed in version 1.2. It seems like the book should mention that manually changing the RATE will effect the quantity dosed each day, so the RATE should be left at the value determined through calibration. It seems like it should also mention that when calibrating the pump it should be set-up in the same location with the same length of tubing and same pumping heights as it will have when running on the tank. When I calibrated mine I just set it on the floor right next to the reservoir and a 500 mL container, and I was not pumping near the height that I am pumping now. I have since corrected this.


I'll see if I can determine where the clicking is coming from. It doesn't bother me too much, and neither does the vibrating. I am just concerned that it will eventually cause something to break. If it does cause something to break I would assume that it would be in the mechanics of the pump rather than in the computer, which would require me to switch to one of your fancy new $75 pumps. It will probably be more cost effective in the long run if, rather than spend the money to ship it and have it repaired and have it returned, I just wait it out and if it breaks then I will have you send me one of your $75 pumps.

[SpectraPure]

That is correct.

History: the original LiterMeter needed to have the RATE set manually with thumbwheel switches. In trying to replicate the original operation, the programmer (me) couldn't imagine that anyone would violate the sanctity of the RATE value that was so obvious to him.

The manual writer (me) didn't check the programmer's GUI logic and just wrote a manual that matched the LM3 operation. Version 1.1 did not last long and the programmer's change in V1.2 precluded the need to mention it in the manual. This single cryptic line is in the paragraph on calibrating:

Variations in pumping height and liquid viscosity will also affect the flow RATE of the pump.

It should have been clearer.

I thought you had a new pump in your unit. If it's the plastic pump, I can almost bet you've developed scored grooves on one or more rollers. They click when they come around to the motor shaft. There are no more spare rollers. Live with it 'till you can't stand it.

Scott
SpectraPure, Inc.

[saltyseaman]

Ahh, I see. Thanks for that tidbit of info.

I really appreciate all of your help! This is a really cool device. The remote pump modules are coming next :D