Chris's Wiki :: blog/sysadmin/MachineRoomTempMonitoring Commentshttps://utcc.utoronto.ca/~cks/space/blog/sysadmin/MachineRoomTempMonitoring?atomcommentsDWiki2022-09-14T12:15:49ZRecent comments in Chris's Wiki :: blog/sysadmin/MachineRoomTempMonitoring.By Hales on /blog/sysadmin/MachineRoomTempMonitoringtag:CSpace:blog/sysadmin/MachineRoomTempMonitoring:2f468ef2d7fca8d77859d86f141299a08ca855bdHaleshttps://halestrom.net<div class="wikitext"><p>If you're going as far as using USB devices and polling them: I'd suggest also taking a look at the DS18B20.</p>
<p>You can get them in pre-made metal pills with wires already attached. Raspis speak 1-wire natively and the sysfs interface is very very simple (it spits the decoded degC out when you read the file). Crimp the 3 wires (or 2 wires + a resistor) onto a header and you're ready.</p>
<p>Alas I suspect you might be thinking of plugging these USB devices into existing servers, rather than adding new computers/SBCs just to do temperature measurements, so this might not suit.</p>
<p>ith this method don't need USB drivers or any vendor-made software. One line of shell is enough to do a reading. Also there will be other SBCs with working 1-wire kernel implementations, so you're not beholden to the ebb and flow of raspi stocking levels.</p>
</div>2022-09-14T12:15:49ZBy Chris Siebenmann on /blog/sysadmin/MachineRoomTempMonitoringtag:CSpace:blog/sysadmin/MachineRoomTempMonitoring:ba9460b51ae19d96d890c1e329d651cfcfb2f90fChris Siebenmann<div class="wikitext"><p>The industrial units all seem to use external probes, quite probably
partly for the reasons your article talks about (although the product
pages also talk about things like putting the probe in a refrigerated
area with the unit outside). However, what you wrote about is definitely
something we'll have to remember for USB-based things like the TEMPer2,
which have an onboard sensor (as well as a probe in their case; some of
the series only have an onboard sensor). Fortunately the TEMPer2 has
somewhat odd results in general so I'm already biased to not trust it
too much.</p>
</div>2022-09-11T10:49:26ZBy Hales on /blog/sysadmin/MachineRoomTempMonitoringtag:CSpace:blog/sysadmin/MachineRoomTempMonitoring:4acb19793160e7877e91c61ab5083371a85be2eaHaleshttps://halestrom.net<div class="wikitext"><p>Ah, sorry. I missed that you are using external probes. That avoids 90% of the problems.</p>
<p>With external probes I would completely trust the manufacturer's datasheet for the product. The only worry left is position relative to aircon vs heat exhaust flows, but it seems like you already have something that works.</p>
<p>If it works for you then stick with it.</p>
</div>2022-09-11T07:46:40ZBy Chris Siebenmann on /blog/sysadmin/MachineRoomTempMonitoringtag:CSpace:blog/sysadmin/MachineRoomTempMonitoring:5586e6b388a1e1cf493ed0db39cad444714da863Chris Siebenmann<div class="wikitext"><p>It's useful for us to have pretty accurate room temperature readings,
because then we can tell the facilities people more about what's going
on (and also have confidence about <a href="https://utcc.utoronto.ca/~cks/space/blog/sysadmin/PrometheusLongHistoryUse">smaller anomalies than outright AC
failure</a>). But, fortunately, as a first line
of defense and alerting, what we care most about is a clear relative
change in temperature. If a sensor reads high or low under normal room
conditions (even extremely so) but will climb up significant when the
AC dies and the room temperature goes up a bunch, we can work with that.</p>
<p>We do have to place the temperature probes in useful places, and we
haven't always been completely successful in that. Moving the existing
probes would be a fair amount of work, so they're probably staying where
they are. We have at least seen their readings go up when the AC has had
problems.</p>
<p>(I don't think we've actually ever tried to carefully cross-check our
existing temperature probe readings against other sources of truth, so
we don't know how accurate they are, although I think they're probably
okay.)</p>
</div>2022-09-11T02:54:20ZBy Hales on /blog/sysadmin/MachineRoomTempMonitoringtag:CSpace:blog/sysadmin/MachineRoomTempMonitoring:92568d5a1654fd4b01989c3ae21458124a8a64a2Haleshttps://halestrom.net<div class="wikitext"><p>I recently wrote about the problems I've had with air temperature sensing devices (especially ones with bigger micros/SoCs such as networked ones). You might find the advice in this useful if/when window shopping for new ones. </p>
<p><a href="https://halestrom.net/darksleep/blog/048_indoorairsensing/">https://halestrom.net/darksleep/blog/048_indoorairsensing/</a></p>
<p>TL;DR: Measuring ambient air temperature is very easy to do wrong, most of the devices I've looked at or used give wildly results different (eg error 5degC) unless you force airflow over them. You can't calibrate this out because position, airflow and self-heating change unpredictably over time.</p>
<p>This might (?) be fine in a closet environment where you can mount it nearer a fan's stream? Or perhaps an error of 5degC doesn't matter too much in your application (whilst in my applications of indoor/human/AC monitoring it's almost all of the expected temperature swing range).</p>
<p>Everything in this market is either IoT (cheap but unreliable) or expensive (might be good, might be trash). Price alone is not a good indicator, I've dealt with many expensive sensors that don't seem like they were tested beyond a simple home LAN with no routing and the proprietary server software running on a dev's laptop for a few hours.</p>
</div>2022-09-11T00:18:34Z