Revision as of 14:54, 5 September 2017

RTD Temperature Sensor

1 General information

MSxxx Overview

2 Mechanics

• Dimensions 60 x 95 x 85mm (109mm including fixing brackets)
• 96mm spacing between brackets
• IP 65
• Solid ABS & PC material

3 RTD Temperature sensor properties

• Handles 100Ω to 1kΩ (at 0°C) Platinum RTDs (PT100 to PT1000)

• 2-wires, 3-wire or 4-wire connection

• 15-Bit ADC Resolution; Nominal Temperature Resolution 0.03125°C (Varies Due to RTD Nonlinearity)

• Total Accuracy Over All Operating Conditions: 0.5°C (0.05% of Full Scale) max

• ±45V Input Protection

• Fault Detection (Open RTD Element, RTD Shorted to Out-of-Range Voltage, or Short Across RTD Element)

• Direct fifth-order linearization for best accuracy

4 Wiring

5 Magnetic Switch Protocol description

MSxxx Generic Magnetic Switch Protocol

6 Radio frames description

MSxxx Generic Application Protocol

6.1 Uplink data Frame format

The uplink payload contains multiple fields: <mask>: bit field on 1 byte indicating the presence of other fields. Bit 7 is always to 1 because the mask is never extended on next byte.

bit 0 : indicates the presence of <nb_meas> field.

bit 1 : indicates the presence of <rtd_temp> field.

bit 2 : indicates the presence of <voltage> field.

bit 3 : indicates the presence of <internal_temp> field.

bit 4 : is reserved.

bit 5 : indicates the presence of <cause> field.

When bit 0 is not set, it means that other fields are present only once (nb_meas = 1).

if (mask.bit0 == 1) :

   <nb_meas>: 1 byte containing the number of measurements which follows.

if (mask.bit1 == 1) :

   <rtd_temp>: 2*<nb_meas> bytes containing the temperature values in 0.1 °C. Each temperature value is a signed integer on 16 bits in big endian [-32768..+32767].

if (mask.bit2 == 1) :

   <voltage>: 2*<nb_meas> bytes containing the voltage values measured by the sensor in millivolts. Each voltage value is an unsigned integer on 16 bits in big endian.

if (mask.bit3 == 1)

  <internal_temp>: 1*<nb_meas> bytes containing the internal temperature values (using MCU internal sensor). Each temperature value is a signed integer on 8 bits in big endian in °C [-128..+127].

if (mask.bit5 == 1) :

   <cause>: 1 byte containing the cause of the uplink frame. It is a bit field:
       Bit 0 indicates a periodic measure
       Bit 1 indicates the high threshold exceeding (temperature > high threshold)
       Bit 2 indicates the high hysteresis exceeding (temperature < high threshold - high hysteresis)
       Bit 3 indicates the low threshold exceeding (temperature < low threshold)
       Bit 4 indicates the low hysteresis exceeding (temperature > low threshold + low hysteresis)
       Bit 5 indicates the measure has been forced manually (with magnetic switch)
   Usually <cause> field is absent when threshold detections are disabled (periodic measures only)

Thus the uplink frame format is <mask><nb_meas><rtd_temp1>...<rtd_tempN><voltage1>...<voltageN><internal_temp1>...<internal_tempN><cause>

Default <mask> value is 0x83 which means that the default frame is <mask><nb_meas><rtd_temp1>...<rtd_tempN>

Some examples (in hexadecimal):

   “820119”: the frame indicates one temperature measurement of +28.1 °C.
   “8302FFCB000C”: the frame indicates two temperature measurements of -5.3 °c and +1.2 °C.

6.2 Downlink Frame format

The sensor configuration contains the following fields:

   <up_frame_mask>: the mask identifying the different fields present in uplink frames (possible values are described in “Uplink data Frame format” section)
   <nb_meas_for_tx>: the number of measures required to trigger a transmission (possible values are [1..8]
   <meas_period>: the period of the measures in <perdiod_unit> seconds(possible values are [600..65535]
   <period_unit>: the unit of <meas_period> in seconds, the resulting period is <meas_perios>*<period_unit> seconds
   <mode>: bit field enabling/disabling the measures (threshold detections and periodic measures)
   <subperiod>: subdivision of period for threshold detection, actual measurement period is (<meas_period>*<period_unit>)/<subperiod> seconds
   <high_threshold>: value of high threshold
   <high_hysteresis>: value of high hysteresis
   <low_threshold>: value of low threshold
   <low_hysteresis>: value of low hysteresis
   <sensor_type>: identifies the type of sensor (PT100/PT1000 and 2/3/4 wires)

It is possible to change the sensor configuration using the Nemeus downlink protocol. The downlink frame must be sent on the MS008 LoRaWAN port (10).

The downlink frame has the following format:

<cmd>: 1 byte containing WRITE_CFG_CMD=0x02

<mask>: bit field on 1 byte indicating the presence of other fields. Most significant bit (bit7) is always to 1 because the mask is never extended on next byte.

Bit0 indicates the presence of <up_frame_mask> field

Bit1 indicates the presence of <nb_meas_for_tx> field

Bit2 indicates the presence of <meas_period> and <period_unit> fields

Bit3 indicates the presence of <mode> and <subperiod> fields

Bit4 indicates the presence of <high_threshold> and <high_hysteresis> fields

Bit5 indicates the presence of <low_threshold> and <low_hysteresis> fields

Bit6 indicates the presence of <sensor_type> field

If (mask.bit0 == 1):

   <up_frame_mask>: 1 byte containing the uplink frame mask

If (mask.bit1 == 1):

   <nb_meas_for_tx>: 1 byte containing the number of measurements required to trigger a transmission

If (mask.bit2 == 1):

   <meas_period>: 2 bytes in little endian (LSB first) containing the period of measurements in <period_unit> seconds
   <period_unit>: 1 byte containing the unit of <meas_period> in seconds (default value is 1 second)

If (mask.bit3 == 1):

   <mode>: 1 byte encoded as follows:
       bit0: enable(1)/disable(0) high threshold detection
       bit1: enable(1)/disable(0) high hysteresis detection (when leaving high threshold state)
       bit2: enable(1)/disable(0) low threshold detection
       bit3: enable(1)/disable(0) low hysteresis detection (when leaving low threshold state)
       bit4: enable(1)/disable(0) periodic measurements
       bit5 to bit7: reserved
   <subperiod>: 2 bytes in little endian containing the period subdivision

If (mask.bit4 == 1):

   <high_threshold>: signed integer on 2 bytes in little endian containing the high threshold in 0.1 °C [-2000..+8000]
   <high_hysteresis>: unsigned integer on 1 byte containing the hysteresis when leaving high threshold state in 0.1 °C [0..255]

If (mask.bit5 == 1):

   <low_threshold>: signed integer on 2 bytes in little endian containing the low threshold in 0.1 °C [-2000..+8000]
   <low_hysteresis>: unsigned integer on 1 byte containing the hysteresis when leaving low threshold state in 0.1 °C [0..255]

If (mask.bit6 == 1):

   <sensor_type>: unsigned integer on 1 byte containing the sensor type [11..16]
       11(0x0B): PT100 2 wires
       12(0x0C): PT100 3 wires
       13(0x0D): PT100 4 wires
       14(0x0E): PT1000 2 wires
       15(0x0F): PT1000 3 wires
       16(0x10): PT1000 4 wires

Thus the downlink frame format is <cmd><mask><up_frame_mask><nb_meas_for_tx><meas_period><period_unit><mode><subperiod><high_threshold><high_hysteresis><low_threshold> <low_hysteresis><sensor_type>.

Some examples in hexadecimal:

   “028182”: set the <up_frame_mask> to 0x82 => the next uplink frames will include the <rtd_temp> field only
   “028E04605401100100”: set <nb_meas_for_tx> to 4, <meas_period> to 21600*<period_unit> seconds, <period_unit> to 1 second and enable periodic measurements only with subperiod to 1 => one measurement every 6 hours and one transmission every 4 measures (every day). Each uplink frame will include 4 measurements

6.3 Power consumption

Please find below a tool to calculate power consumption vs number of measures and transmissions.