Multiple NCD sensors reading is 25-30F when temp is 5F

I have two brand new NCD temp sensors (PR58-1_MQTT) and they tested correctly at ambient temps, but are both reading 20-25F degrees higher than actual when in our freezers. We have multiple analog and digital thermometers sitting right next to them reading 5F when they are reporting 25-30F.

These devices are rated down to -40C so we are well within the range. Does anyone have any idea what is going on?

Hi Rob,

How long ago did you purchase these devices? If they were very early production units they may be missing a solder bridge. If you can provide an up close photo of the board inside the enclosure I should be able to see if the solder bridge is in place or not.

Purchased one unit December 22, 2022 and four units February 3, 2023. Here are three photos of one of the offending units. Do you see anything awry? If so, could you let me know what so I can check the other units?

Hi Rob,

Thank you, from the files I was able to Confirm that the PWR/I2C solder pads are solder bridged in the PWR position as required.

I will try to perform some testing here on my side to see if I can replicate this issue. I will report back, if a firmware update is required I’ll push the necessary firmware updates and you can update your devices at that time.

Thanks Travis. Please keep me posted. We have five units here that are waiting to go into our freezers and really hoping they will work as advertised.

Hi Travis, any luck? Do you have an estimate on timing? We’re really hoping to get our freezers equipped with sensors by end of week and if the NCD ones aren’t going to be functional I’ll need to go back to square one with another vendor. I hope you can figure something out!

How frequently are you taking the samples?
can you share the values/chart after putting it in the freezer?
@TravisE_NCD_Technica did you get a chance to test it in the freezer?

I talked to @TravisE_NCD_Technica yesterday on the phone and he said he hoped to test it in a freezer by early next week and report back.

@Anil_Bhaskar taking samples every minute. Here is a chart from today:

looks like the freezer is opening and closing a few times and staying open for a long time.
temp chart is in F?

I’ve been running a test in a freezer here for a few hours. I am not seeing any spikes in temperature:

I will let this unit continue to run in the freezer over the weekend to see if there are any anomalies.

Our temp is in F and the freezer thermostat is set to 5F. Two other sensors are reading 5F that are right next to the NCD sensor. It is definitely 5F in there.

The spikes are from us opening the door, yes.

@TravisE_NCD_Technica can you set your freezer somewhere between 0-5F? The screenshot of the chart you shared reads 29.9F, which is close to refrigerator temp, not freezer temp (0-5F).

After running the sensor over the weekend the log looks to be accurate with no false readings. The spikes are from the compressor in the fridge turning on/off which cycles the temperature between around -2 and -10C.

I couldn’t get the freezer down any lower(it’s just a mini fridge freezer). However there should not be a significant difference in your setup.

I will continue to investigate today to see if I can replicate the failures you are seeing.

Could you find a freezer to test at 0-5F? I don’t know what else it could be as this is two units both reporting 20+F higher than actuals when at the 0-5F range. We’ve already sunk a lot of time configuring all 5 units and would hate to have to start again with a different vendor. But, we have a time pressure to get monitoring in these freezers so we don’t lose any product if the power goes out or a compressor fails.

I moved the sensor to our deep freezer. I will report back shortly. I’m not sure how cold it actually is.

Just an update I got the sensor transferred to the deep freeze in the house. You can see on the chart the temperature went up and down in the mini fridge. Seems to be holding steady now around 4.9F. The spike you see was me taking the sensor out of the mini fridge in my office and transferring it to the deep freeze.

I’ll keep you updated but so far over the past hour everything looks normal.

I’m very perplexed. Does this have firmware 1.0.1 from GitHub - ncd-io/WiFi_MQTT_Temperature_Firmware?

I see the legend up top says temperature_c but the panel in the bottom-left says 4.9F. Can you confirm that you’re indeed pulling in temperature_f and the legend label is a typo?

  1. are you reading the same readings on all ncd sensors if they are installed in the same freezer?
  2. install all 5 sensors in the freezer at the same location and take readings for 1hr.

If yes, then I think the sensor is good it could be the meter.

The sensor reports temperature_c and temperature_f. The graph is showing temperature_c, bottom left label is most recent temperature_f and bottom label is temperature_c.

Here is an updated dashboard view where the line chart is based on the temperature_f variable.

I believe you just updated your firmware within the past few days. I have not made any changes since then so it should not be a firmware version issue.

Hi Rob,

Since I’m not able to replicate here I sent you a private message with credentials. Can you enter those into one of the sensors so it reports to my broker and I can monitor the raw data?

Also are you using the 12VDC power supply we provided to power the sensors?