Stratification occurs rapidly if you don't have your ice at all levels of your container. Ice floats, warmer water sinks.
On Tue, Jan 17, 2017 at 3:15 AM, Tom <[email protected]> wrote: > You will need to calibrate the sensors to get real/absolute > measurements out of these devices, in my experience. > I used them for datalogging and they were +-3C between the three of > them I had. > They were self heating by the read process, so you need to let them > stabilize before calibrating and then read them at the same (slow > > 60s) intervals as when calibrating. > I calibrated them to 0C and 60C, determining offset and scaling for > each of them. Although the thermometers were not very linear to this > simple calibration, they were OK to +- about 1C within the range. > I would highly recommend the Maxim DS18B20 as mentioned in the link by > Chuck if you need something more accurate. They cost under $2 in the > waterproof version. > Hat-down to the analog designers @ Maxim designing them so precise > within this wide temperature and voltage range (±0.5°C Accuracy from > -10°C to +85°C @ Vdd=3-5.5V) <-- the probe + reference + A/D convertor > are at the same hot/cold temperature and at variable voltage for about > $1 per sensor delivered. Amazing, in my opinion. > I hope it helps, Tomas > On Mon, 2017-01-16 at 23:48 -0800, Michael C. Robinson wrote: > > I am using a Raspberry Pi 3 2016 Model B. > > > > I'm trying to use USB TEMPer2 Thermometers to detect the temperature > > of ice water and the temperature of nearly boiling water. I am not > > getting the correct temperatures. > > > > pi@raspbypi:~/project $ cat temper-pi.txt > > http://www.linuxjournal.com/content/temper-pi > > pi@raspbypi:~/project $ > > > > pi@raspbypi:~/project $ lsusb > > Bus 001 Device 010: ID 0c45:7401 Microdia > > Bus 001 Device 009: ID 0c45:7401 Microdia > > Bus 001 Device 008: ID 0c45:7401 Microdia > > Bus 001 Device 007: ID 0409:0058 NEC Corp. HighSpeed Hub > > Bus 001 Device 005: ID 0a81:0205 Chesen Electronics Corp. PS/2 > > Keyboard+Mouse Adapter > > Bus 001 Device 011: ID 0c45:7401 Microdia > > Bus 001 Device 006: ID 0c45:7401 Microdia > > Bus 001 Device 004: ID 0409:0058 NEC Corp. HighSpeed Hub > > Bus 001 Device 003: ID 0424:ec00 Standard Microsystems Corp. > > SMSC9512/9514 Fast Ethernet Adapter > > Bus 001 Device 002: ID 0424:9514 Standard Microsystems Corp. > > Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub > > pi@raspbypi:~/project $ > > > > pi@raspbypi:~/project $ lsusb -t > > /: Bus 01.Port 1: Dev 1, Class=root_hub, Driver=dwc_otg/1p, 480M > > |__ Port 1: Dev 2, If 0, Class=Hub, Driver=hub/5p, 480M > > |__ Port 1: Dev 3, If 0, Class=Vendor Specific Class, > > Driver=smsc95xx, 480M > > |__ Port 2: Dev 4, If 0, Class=Hub, Driver=hub/4p, 480M > > |__ Port 1: Dev 6, If 0, Class=Human Interface Device, > > Driver=, 1.5M > > |__ Port 1: Dev 6, If 1, Class=Human Interface Device, > > Driver=, 1.5M > > |__ Port 4: Dev 11, If 0, Class=Human Interface Device, > > Driver=, 1.5M > > |__ Port 4: Dev 11, If 1, Class=Human Interface Device, > > Driver=, 1.5M > > |__ Port 3: Dev 5, If 0, Class=Human Interface Device, > > Driver=usbhid, 1.5M > > |__ Port 3: Dev 5, If 1, Class=Human Interface Device, > > Driver=usbhid, 1.5M > > |__ Port 4: Dev 7, If 0, Class=Hub, Driver=hub/4p, 480M > > |__ Port 1: Dev 8, If 0, Class=Human Interface Device, > > Driver=, 1.5M > > |__ Port 1: Dev 8, If 1, Class=Human Interface Device, > > Driver=, 1.5M > > |__ Port 2: Dev 9, If 0, Class=Human Interface Device, > > Driver=, 1.5M > > |__ Port 2: Dev 9, If 1, Class=Human Interface Device, > > Driver=, 1.5M > > |__ Port 4: Dev 10, If 0, Class=Human Interface Device, > > Driver=, 1.5M > > |__ Port 4: Dev 10, If 1, Class=Human Interface Device, > > Driver=, 1.5M > > pi@raspbypi:~/project $ > > > > pi@raspbypi:~/project/temper-python $ cat take_temps.bash > > #!/bin/bash > > > > while (true) > > do > > > sudo temper-poll -p > > > sleep 10 > > done > > > > @raspbypi:~/project/temper-python $ ./take_temps.bash > > Found 5 devices > > Device #0 (bus 1 - port 4): 25.1°C 77.1°F > > Device #1 (bus 1 - port 2): 24.1°C 75.3°F > > Device #2 (bus 1 - port 1): 21.5°C 70.7°F > > Device #3 (bus 1 - port 4): 23.8°C 74.9°F > > Device #4 (bus 1 - port 1): 23.2°C 73.8°F > > Found 5 devices > > Device #0 (bus 1 - port 4): 25.1°C 77.1°F > > Device #1 (bus 1 - port 2): 24.1°C 75.3°F > > Device #2 (bus 1 - port 1): 21.5°C 70.7°F > > Device #3 (bus 1 - port 4): 23.8°C 74.9°F > > Device #4 (bus 1 - port 1): 23.2°C 73.8°F > > Found 5 devices > > Device #0 (bus 1 - port 4): 25.1°C 77.1°F > > Device #1 (bus 1 - port 2): 24.1°C 75.4°F > > Device #2 (bus 1 - port 1): 21.5°C 70.7°F > > Device #3 (bus 1 - port 4): 23.8°C 74.9°F > > Device #4 (bus 1 - port 1): 23.2°C 73.8°F > > Found 5 devices > > Device #0 (bus 1 - port 4): 25.1°C 77.1°F > > Device #1 (bus 1 - port 2): 24.1°C 75.4°F > > Device #2 (bus 1 - port 1): 21.5°C 70.7°F > > Device #3 (bus 1 - port 4): 23.8°C 74.9°F > > Device #4 (bus 1 - port 1): 23.2°C 73.8°F > > Found 5 devices > > Device #0 (bus 1 - port 4): 25.1°C 77.1°F > > Device #1 (bus 1 - port 2): 24.2°C 75.5°F > > Device #2 (bus 1 - port 1): 21.5°C 70.7°F > > Device #3 (bus 1 - port 4): 23.8°C 74.9°F > > Device #4 (bus 1 - port 1): 23.2°C 73.8°F > > Found 5 devices > > Device #0 (bus 1 - port 4): 25.1°C 77.1°F > > Device #1 (bus 1 - port 2): 24.2°C 75.5°F > > Device #2 (bus 1 - port 1): 21.5°C 70.7°F > > Device #3 (bus 1 - port 4): 23.8°C 74.9°F > > Device #4 (bus 1 - port 1): 23.2°C 73.8°F > > ^C > > > > Please note the following changes to Raspbian, Jessie I believe... > > > > pi@raspbypi:~/project/temper-python $ cat /boot/cmdline.txt > > dwc_otg.lpm_enable=0 console=serial0,115200 console=tty1 > > root=/dev/mmcblk0p7 rootfstype=ext4 elevator=deadline fsck.repair=yes > > rootwait quiet splash plymouth.ignore-serial-consoles > > usbhid.quirks=0x0c45:0x7401:0x4 > > > > pi@raspbypi:~/project/temper-python $ cat /etc/udev/rules.d/99- > > tempsensor.rules SUBSYSTEMS=="usb", ACTION=="add", > > ATTRS{idVendor}=="0c45", ATTRS{idProduct}=="7401", MODE="666" > > > > The above changes allow non non root users to use temper-python and > > they should prevent problems with the sensors being identified as > > keyboards? > > > > The following is an excerpt out of dmesg: > > > > [ 206.199665] usb 1-1.2.1: new low-speed USB device number 14 using > > dwc_otg > > [ 206.317607] usb 1-1.2.1: New USB device found, idVendor=0c45, > > idProduct=7401 > > [ 206.317619] usb 1-1.2.1: New USB device strings: Mfr=1, Product=2, > > SerialNumber=0 > > [ 206.317626] usb 1-1.2.1: Product: TEMPer2_M12_V1.3 > > [ 206.317633] usb 1-1.2.1: Manufacturer: RDing > > [ 206.409673] usb 1-1.2.4: new low-speed USB device number 15 using > > dwc_otg > > [ 206.527634] usb 1-1.2.4: New USB device found, idVendor=0c45, > > idProduct=7401 > > [ 206.527645] usb 1-1.2.4: New USB device strings: Mfr=1, Product=2, > > SerialNumber=0 > > [ 206.527653] usb 1-1.2.4: Product: TEMPer2_M12_V1.3 > > [ 206.527659] usb 1-1.2.4: Manufacturer: RDing > > > > I noticed that the Linux Journal article is old and that the sensors > > I > > have are likely newer than when the article was written. The seller > > said Linux compatible, but is that true? > > _______________________________________________ > > PLUG mailing list > > [email protected] > > http://lists.pdxlinux.org/mailman/listinfo/plug > _______________________________________________ > PLUG mailing list > [email protected] > http://lists.pdxlinux.org/mailman/listinfo/plug > _______________________________________________ PLUG mailing list [email protected] http://lists.pdxlinux.org/mailman/listinfo/plug
