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2di sensors

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Sensors used with the TV2 monitors are of two different types:

  1.  Wired sensors for TV2-202 monitors
    1. DD1 Temperature only (-40°C to 120°C)
    2. TSMRH3001 Temperature/humidity (-20°C to 80°C, 5% to 90%)
    3. WDP2 Differential pressure sensor (±0.5″wc)
    4. TC-x Thermocouples (200°C to 1250°C, type dependent)
  2. Wireless Sensors for TV2-201 monitors
    1. WS4HETM External Thermistor (-30°C to 80°C)
    2. WS4HITMIHM Temperature/humidity (-20°C to 80°C, 5% to 90%)
    3. WS4HTC-x Thermocouples (200°C to 1250°C, type dependent)

All sensors designed to work with the TV2 monitors are digital.  This means that each has an analog to digital converter built into the sensor, so technically the sensors take readings as an analog sensor but the signal is converted to a digital value before being transmitted to the TV2 monitor.  This is important because when a digital signal is transmitted via a direct wire it is much more unlikely to be affected by noise generated by the external environment.

We make every effort to insure that all 2di sensors meet or exceed the accuracy requirement necessary meet all regulatory and industry standards that apply to their intended uses.  For example, many of our customers use the TV2 sensors to monitor, log and alarm refrigerators and freezers storing vaccines.  The CDC as well as certain industry groups such as JCAHO, recommend that temperature sensors used to monitor refrigerator and freezer temperatures have an accuracy of at least ±0.3°C.  All of our temperature sensors except thermocouples, which are used for extreme temperature not necessary for vaccine storage, meet or exceed this level of accuracy, (see table below).

  1.  Wired sensors for TV2-202 monitors
    1. DD1 Temperature only (±0.30°C)
    2. TSMRH3001 Temperature/humidity (±0.3°C, ±1.5%)
    3. WDP2 Differential pressure sensor (±0.002″wc)
    4. TC-X Thermocouples (t-type ±1.0°C, E, J, K types ±2.2°C)
  2. Wireless Sensors for TV2-201 monitors
    1. WS4HETM External Thermistor (±0.3°C)
    2. WS4HITMIHM Temperature/humidity (±0.3°C, ±1.5%)
    3. WS4HTC-x Thermocouples (t-type ±1.0°C, E, J, K types ±2.2°C)

What role does the TV2 monitor play in sensor accuracy.  The TV2 monitor whether the TV2-202 or the TV2-201 does have a very small impact on the 2di sensors, but it is in the range of 0.1% of the reading.  This means that it could affect the sensor accuracy by that amount, so a DD1 sensor could by ±0.3001°C.  This amount is so small that it can not be measured except with an extremely accurate scientific instrument and is within the limits prescribed by CDC, FDA, JCAHO, and other certifying agencies.  This means that if sensors are re-calibrated by 2di it is not necessary to send the TV2 monitor with the sensor.

How often do sensors need to be re-calibrated?

DD1 – Never needs to be re-calibrated, however some certifying agencies require sensors to be re-calibrated every year or two.  We generally put a date two years in the future on our calibration certificates as the re-calibrate date.

TSMRH3001 – Never needs to be re-calibrated. Under normal operation, the sensor may drift to ~0.1%RH/year. We qualify the HS3001 for 10years operation.  The temperature part of this sensor also has minimal drift.  We put a date two years in the future on our calibration certificates as the re-calibrate date.

The re-calibrate date listed on 2di Calibration certificates is listed because most certificating agencies want to see a re-calibration date and a two year re-calibration date seems to make them happy.  We could put a date of 5 years for re-calibration certificate but the agencies would balk.  They do not yet grasp that modern digital sensors if manufactured correctly, do not drift so they really never need to be calibrate.  The exception to this is thermocouple sensors which do drift over time.