Trying to follow a profile that bounces around can be challenging if not downright frustrating. If you're observing weirdness in your temperature readings, there can be a few reasons for this. Broadly speaking these fall into one of two categories: electronic noise or mechanical damage related.
Here are a few things to check if you're experiencing any of these issues.
Sudden jumps in temperature or spikes
The most common reasons for this are:
Using a grounded thermocouple
Mechanical damage to a thermocouple wire
Since we only stock and sell ungrounded thermocouples, the most common issue we run into is the later - mechanical damage.
The test for this scenario is quite easy. Simple wiggle the TC wire around in different locations. Start where it plugs into the Data Bridge and check all the way to where it enters the TC shaft. Thermocouples are comprised of two wires within the sheath. If the wires are damaged inside the sheath or if they loose contact anywhere, readings will not be correct. The telltale sign is that the readings will change as you move the wire around… this usually means that the wires are making and then breaking contact resulting in "spiking" readings.
If you're not sure whether you have a grounded or ungrounded thermocouple, there are also a couple of tests to perform.
First, if you're using a laptop, unplug the laptop from the power cable and run off battery power. If you notice the temperature reading change when the laptop is plugged in vs. running from battery, you have a grounded TC and will need to install and ungrounded TC.
Another test is to plug the TC into a handheld TC readout such as this one from Fluke. As long as the handheld meter runs from battery power, it will eliminate any ground loop issues which is what these tests are trying to accomplish.
Constantly bouncy temp profiles
When profiles seem to have a bounciness that extends through the entire roast and across all the thermocouples you've installed, this is a strong indication of electronic noise or interference.
Often times we see this when a data bridge is placed near large electronic hardware, e.g., control panel for your roaster, or fan motor.
Another possible but less common issue affects our older legacy 1-input Data Bridge. The cover is such that it's possible for charged particles (e.g., chaff) to get into the circuitry, which is bad, but easy to fix. To remedy this:
Unplug both the USB cable and TC connector(s) from the Data Bridge.
Using compressed air or some very strong breaths, try to blow out any particle building from inside the case
If #2 doesn't work, open the plastic enclosure and blow off the circuitry more directly