Accuracy of Ranco Digital Controllers

[Bryan]

Can anybody vouch for the accuracy of the Ranco Dual Stage Digital Controllers. I find a lot of these digital type controllers/monitors are really innacurate, often 2-3 degrees off in terms of temperature measurement.

[pr0nd3xtr]

BUMP

Just got one so I would like to hear opinions on this as well.

[Puffer Daddy]

What perfect timing...

I got one as well...but I lost my directions. By chance, can someone tell me how to set it up to cut off heaters at 80 and turn a fan on at 83?...sorry, my wife can certianly vouch for me losing things...

[pr0nd3xtr]

Puffer Daddy: Press the set button until you get S1 and the temp is flashing. Set this to the temp you want the heater to come on. Press set again, and set the differential (I dont know what this does so I set it to 1), press set to choose between C1 (cooling mode) or H1 (heating mode). Do the same for S2 except you will choose either C2 or H2.

HTH

BTW if anyone can tell me what the differential is for I would appreciate it

[pjf]

Unlike many aquarium controllers, the Ranco ETC cannot be calibrated if it drifts. How accurate is it? If you own a Ranco and a glass thermometer, I’d appreciate your posting the following:

1. Temperature as displayed by your Ranco
2. Temperature as measured by your glass thermometer
3. Number of month or years that you have used your Ranco

Thanks!

[sabodish]

mine is within a half a degree when i check it with my digital.

[mg426]

Mine is right on with a floater that I have.

[RGibson]

Take a glass of ice water more ice then water put the probe in the glass and stir you should get 32 deg

[pjf]

Good idea! I understand that the Ranco ETC has a range from -30 degrees to +220 degrees Fahrenheit. This means that the probe may also be gauged against boiling water at sea level (212 degrees?).

[Donw]

They do have a differential adjustment so if its off a little just adjust the differential.

Don

[RicGio]

Ran mine for 5 years and it was always dead on.

[purplereef]

How do you adjust the differential?

[miatawnt2b]

Ranco controllers are going to be dead on. They are industrial controllers used to control things like walk-in coolers at blood banks/hospitals and such where the temp must be super accurate. Don't confuse one of these controllers with its aquarium counterpart you can pick up for $10 nor your house thermostat.

-J

[BeanAnimal]

They can be +/- 1 degree according to the specs. So if you put 100 of them in the same environemnt you should expect to see a rang of about 3 degrees maximum between the highest and lowest reading. The specs and reality are two different things. In most cases the RANCOS have a much tighter tolerance than the published specs! On average (in reality) you would be looking at 1 to 1.5 degrees max difference between the highest and lowest readings out of a large sample.

This is MORE than accurate enough for a fish tank and much more accurate than your typical "floater" or low grade thermometer.

Remember folks we are attempting to keep our tanks in an acceptable RANGE that is fairly wide, not at a specific dead nuts temperature.

The RANCO controller is very dependable and that is what is important.

[pjf]

I’ve never used the Ranco ETC but the differential is usually the point at which a heater (or chiller) will be activated. For example, if your set point is 75-degrees and your differential is 5-degrees, then your heater will switch ON at 70-degrees (= 75 - 5) and switch OFF upon reaching the set point.

Are there any links to Ranco ETC specifications regarding its accuracy? This is becoming important as many aquarists are relying on their controller as a thermometer.

[BeanAnimal]

PJF why do you insist on beating this horse when you already know the answers?

1) Yes the "differential" or "Hysteresis" determines the range between the thermostats ON and OFF settings.

2) I already told you what the specifications were. Again, +/- 1 Degree F. That means you either do not read or want to discredit me by showing peopke that you have ignored what I posted. Good grief.

3) It is not AT ALL important. Once again, we are shooting for a temperature within a broad range, not an exact. It simply does not matter. If your thermometer or controller says 77 and the tank is actually 78.2 who cares. If you run on the ragged edge at a normal temp around 84 degrees, then you may be more concerned, but your time would be better spent finding a way to run at a slightly lower temperature than it would be obsessing about the number of significant digits that your thermometer can be calibrated to.

[RGibson]

Ranco are some of the best controls that you can buy have use them on chillers for many years. And i used them on my reef tank.

[pjf]

Originally posted by BeanAnimal
They can be +/- 1 degree according to the specs. So if you put 100 of them in the same environemnt you should expect to see a rang of about 3 degrees maximum between the highest and lowest reading. The specs and reality are two different things. In most cases the RANCOS have a much tighter tolerance than the published specs!

Any links to the published specifications?

[BeanAnimal]

NO PJF, no links. Your obsession with "published links" baffles me. In this case why does it matter? You can certainly call them and speak to an engineer.

But lets use some basic logic here.

If the minimum hysteresis is +/- 1 degree F. Then any amount of precision beyond 1 F is pretty much useless (esp for our purposes). The unit only displays full degrees, not tenths.

We can of course show that higher accuracy does have some effect on the display, but how much?

Lets assume it rounds for the display (the other option would be truncation). So if the true temperature is 77. 8 and the precision was +/- 1 degree then the display could read 77, 78 or 79 degrees. At no point will the display ever read more than about 1.5 degrees different than the actual temperature. Well within the acceptable range of precision. In the real world that range is likely less than a degree.

Here is the important part PJF!

If the precision of the unit was .5 degrees, then the display would still show 2 possible temperatures for some readings!

If the precision of the unit was .001 degrees, then the display WOULD STILL SHOW 2 possible temperatures for some readings!

Making the sensor several times more accurate only makes the display slightly more accurate. At best, even with a +/- .001 accuracy, you can only be confident that that display is within .5 degrees!

With a +/- .5 degree precision, the display will be within about .75 degrees of the actual temperature worst case! In most cases it will be within less than .25 degrees.

With a +/- 1 degree precision, the display will be within about 1.49 degrees of the actual temperature worst case! In most cases it will be within less than a degree.

We can carry out the same exercise for truncated displays as well.

If you are having trouble wrapping your head around this, I can build you a very basic spreadsheet to demonstrate the points being made.

The base point remains the same. It just does not matter. The reliability is important aspect. If your concerned about the real world difference between a degree F, then you may want to rethink your understanding of tank temperature as it relates to the real world. We are not conducting a precision lab experiment that requires heat calcs to be accurate.

[Donw]

Originally posted by purplereef
How do you adjust the differential?

Here ya go pretty straight forward.
http://www.honeyrunapiaries.com/stor...structions.pdf

[Donw]

I agree they are never going to be 100% accurate but nothing in its price range would be. Ranco's are industrial controllers, thats their biggest appeal and the reason they are so reliable. We are performing the same demanding tasks that they are designed to to do.
They are just plain one of the best products out there for the job and beat anthing made for the aquarium industry hands down.

Don

[pjf]

There are many aquarium electronics, such as pH meters, salinity monitors, and temperature controllers that can be calibrated dead-on with reference fluids or glass thermometers. Accuracy is usually not an issue unless you have a device, such as the Ranco ETC, that cannot be field-calibrated and cannot be corrected for drift.

Per Honey Run Apiaries, the distributors of the Ranco ETC, one source of inaccuracy is the electrical source. Household voltage can vary with locale and circuit voltage can vary with power-hungry appliances. The standards for household wiring are not as stringent as those for commercial wiring where HVAC circuits are often isolated.

Another source of inaccuracy is the temperature range supported. The Ranco supports a wide 250 degree (-30 to +220) range. Other controllers support a narrower range that serves to lessen the potential error.

Here’s a cheap temperature control system that rivals the Ranco ETC: a glass thermometer and two small Eheim Jager heaters, each delivering about 1 watt/gallon. The heaters can be calibrated periodically with the thermometer and you have limited protection from a single heater failure.

Why is this important? It is because many aquarists want to use their controllers as thermometers and because the competition offers controllers that can be field-calibrated for accuracy. You have lots of choices (http://www.aquariumcontrollers.com/), so shop around this holiday season!

[BeanAnimal]

There are many aquarium electronics, such as pH meters, salinity monitors, and temperature controllers that can be calibrated dead-on with reference fluids or glass thermometers. Accuracy is usually not an issue unless you have a device, such as the Ranco ETC, that cannot be field-calibrated and cannot be corrected for drift.

You keep insisting that field calibration is important and that is simply not at all true.

We are shooting for a broad target PJF, not an exact temperature. How many times and ways does this have to be explained.

Per Honey Run Apiaries, the distributors of the Ranco ETC, one source of inaccuracy is the electrical source. Household voltage can vary with locale and circuit voltage can vary with power-hungry appliances. The standards for household wiring are not as stringent as those for commercial wiring where HVAC circuits are often isolated.

What nonsense. How does the code being more "stringent" affect the load? Secondly, residential and commercial are under the same code and for the most part differ very little with regard to circuit topology.

But now that you opened the can of worms, lets look at your statement in a little more detail! You list yourself as an Electrical Engineer and should therefore know that a commercial facility has a much more diverse power signature than any home. Harmonics due to ballasts, transformers, large motors, shared neutrals and ground loops are very commonplace. You blowing smoke if you want us to believe that the RANCO will be more accurate on a dedicated commercial HVAC circuit as opposed to a home shared circuit. Honestly, PJF you should know better. This is getting silly and you should be ashamed of even making such an assertion.

Another source of inaccuracy is the temperature range supported. The Ranco supports a wide 250 degree (-30 to +220) range. Other controllers support a narrower range that serves to lessen the potential error.

Now we are grasping at straws aren't we! How many times do we have to go over this. WHO CARES ABOUT THE ERROR, IT IS INSIGNIFICANT IN THE SCOPE OF OUR SYSTEMS! As mentioned the error is +/- 1 degree. Who cares.

Here’s a cheap temperature control system that rivals the Ranco ETC: a glass thermometer and two small Eheim Jager heaters, each delivering about 1 watt/gallon. The heaters can be calibrated periodically with the thermometer and you have limited protection from a single heater failure.

No PJF, it does not come close to rivaling the RANCO's reliability or ease of use. Using a RANCO with (2) small heaters is the best option. There is no need to calibrate the heaters or the RANCO. Simply set the RANCO and adjust the knobs on the heaters to just slightly above the point where the RANCO turns them off. You now have a failsafe system that has at least 2 layers of over temperature protection. Do we have to argue this again as well? Do we need to point out that your rival system relies on the thermostats in the heaters and that alone makes the setup MUCH more failure prone? Do we have to point out that using the RANCO to turn the heaters on and off is magnitudes more reliable than relying on the internal thermostats. Why do I have to point out the same flawed logic over and over?

Why is this important? It is because many aquarists want to use their controllers as thermometers and because the competition offers controllers that can be field-calibrated for accuracy. You have lots of choices (http://www.aquariumcontrollers.com/), so shop around this holiday season!

It is only important if you feel that you need to know the EXACT temperature of your water. I can sleep well knowing that my tank is 80 +/- 1 degree. My fish don't care, nor do I. There are much more important things to worry about than a few tenths of a degree. Do you send your lab thermometer off to be tested against a certified standard? I mean if your going through all the trouble of calibration, then you should do it right! I have been accused of over thinking things, but this honestly takes the cake.

Shall we talk about the fact that a RANCO is more reliable than an aquarium controller? That can be very easily shown. Do we need to mention that a RANCO is around $75 new and you can't shake a stick at an aquarium controller for that?

Shall we put this silly thread to rest now?

[pjf]

Originally posted by BeanAnimal
As mentioned the error is +/- 1 degree.

Per the distributor of the Ranco ETC, Honey Run Apiaries, the error can be larger depending on variations in the electrical source. If you disagree, please argue with the distributor.

Originally posted by BeanAnimal
Shall we talk about the fact that a RANCO is more reliable than an aquarium controller? That can be very easily shown.

Then it should be easy to post links to support your statements.

Whether you agree with Honey Run Apiaries or not, my recommendation is to "shop around." There are plenty of choices for aquarium temperature controls. The Eheim Jager heaters are cheap and have something the Ranco does not have. They can be calibrated.

[BeanAnimal]

It is frustrating that you ignore any point that shows you to be wrong and instead try to change the argument to an irrelevant tangent.

Per the distributor of the Ranco ETC, Honey Run Apiaries, the error can be larger depending on variations in the electrical source. If you disagree, please argue with the distributor.

Once again PJF you have quoted a source and taken it out of context to benefit your argument.

Lets take this IN CONTEXT:

1) Who said I disagreed with the concept that power quality could affect the unit? Power quality affects ALL electronics PJF. Your 120V wall clock is affected, your digital clocks are affected. The scan rate on your TV is affected. Just about any device that uses an analog probe will be affected by the input source. Your an EE PJF, you know (should know?) that the RANCO and every other analog probe is a simple voltage/current comparator and thus affected by the source supply.

Of course we can build around the problem and design a unit with MORE precision and de-couple it from source problems. It is pointless as already shown here and in other threads.

2) The BIGGER problem is that you have taken a fact and then twisted it around your own deceptive reasoning. You said [SIC] "The problem will be more prevalent in a home environment due to power problems that are not present in commercial environments where the code is much stricter and the unit will be on a dedicated HVAC circuit." That is complete and utter nonsense. You know it, I know it, and any person that knows anything about electricity knows it. Did you throw it out there thinking we were all stupid?

Lets be clear so that the othe readers are not deceived by your comments:
Folks, Commercial/Industrial power is almost always MUCH worse than what you have flowing out of your homes panel. The spikes, harmonics, phase anomalies, ground loops, and unfiltered noise are a constant battle in commercial facilities. That is EXACTLY why RANCOS and similar industrial/commercial equipment are built so bulletproof.

So no, I have no argument with "Honey Run Apiares". My argument is with your distortion of facts and subsequent application of your derived truth.

Then it should be easy to post links to support your statements.

Who needs links to understand basic logic? We go through this exercise over and over.

Lets give it a try again: (We did this in 2 other threads).

1A) A RANCO is a dedicated temperature controller. It does one thing and does it well. It has a supply input, a load output and a probe input. That is (3) interfaces that could contribute to, or cause a failure.

1B) An "aquarium controller" has at least 1 supply input, several load outputs and several probe inputs. There are MANY interfaces that could contribute to, or cause a failure. The unit is simply MORE exposed.

This is basic design logic and as an EE you know (should know) it. The more nodes that are tied to a system, the greater chance the system has to fail.

The argument is over already, as the point has been made. But lets go on.

2A) The RANCO is hard coded with the only user input being set points. There is little room for user error. The driving variable is the single probe input. Bugs are easy to find and remove because the code is fixed and simple.

2B) The aquarium controller is scriptable with user input. There are MANY intertwined aspects of the units operation and the source code is much more complex. There are MANY driving variables that interact with the code. These include multiple inputs and user crafted scripts. This is a complex system that is MUCH more prone to firmware bugs AND human errors in programming logic. Debugging is much harder as all interactions can not be predicted. Human programming error is also a large problem (remember those complex interaction?).

The is really over, as the point has been succinctly made. But lets go on.

3A) The RANCO has a rather small component count and is made to withstand rugged commercial/industrial use. The circuit design is mature and proven. Low component count and robust circuit design mean low failure rates.

3B) The aquarium controller has a MUCH higher component count, much of it delicate. The circuits are NOT designed around rugged commercial/industrial use and do not have a long track record. On the contrary some units are very prone to outside interference from ballasts and lighting.

You list yourself as an EE, this stuff SHOULD be common sense to you PJF. I am baffled that somebody with your credentials would continue to make the arguments that you make.

Whether you agree with Honey Run Apiaries or not, my recommendation is to "shop around." There are plenty of choices for aquarium temperature controls. The Eheim Jager heaters are cheap and have something the Ranco does not have. They can be calibrated.

We have already covered each of those statements. Calibration is certainly not important, nor is the fact that your mains power can affect the operation of electronics.

Time to pack this one in PJF.