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2021-10-11T09:34:25Z

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[[File:.png|thumb|400px|NH3 Gas Sensor]]

= General information =
{{:NIS Overview}}

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

= NH3 Gas sensor properties =

* 0 to 100ppm ± 8ppm ± 3% (Conditions : 25°C / Hygrometry : 50% / Pression 1013 mbar)
* Humidity Range 0 to 95% rh non-condensing
* Sensor Temperature Range -20°C to +50°C
* Temperature compensation

= Magnetic Switch Protocol description =
{{:NIS Generic Magnetic Switch Protocol}}

= Radio frames description =
{{:NIS Generic Application Protocol}}

== 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 <analog_meas> 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) :
<analog_meas>: 2*<nb_meas> bytes containing the analog measure values in ppm. Each measure 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 (analog_meas > high threshold)
Bit 2 indicates the high hysteresis exceeding (analog_meas < high threshold - high hysteresis)
Bit 3 indicates the low threshold exceeding (analog_meas < low threshold)
Bit 4 indicates the low hysteresis exceeding (analog_meas > 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><analog_meas1>...<analog_measN><voltage1>...<voltageN><internal_temp1>...<internal_tempN><cause>

Default <mask> value is 0x8A which means that the default frame is <mask><analog_meas><internal_temp>

Some examples (in hexadecimal):

“8A000113”: the frame indicates one analog measurement of 1ppm, with an internal temperature of 19°C.
“8A000E14”: the frame indicates one analog measurement of 14ppm, with an internal temperature of 20°C.

== 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
<pwr_on_duration>: value in ms to wait between sensor power-on and measure reading

It is possible to change the sensor configuration using the Nemeus downlink protocol. The downlink frame must be sent on the MS008 LoRaWAN port (11).

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 <pwr_on_duration> 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):
RESERVED

If (mask.bit4 == 1):
RESERVED

If (mask.bit5 == 1):
RESERVED

If (mask.bit6 == 1):
RESERVED

Thus the downlink frame format is <cmd><mask><up_frame_mask><nb_meas_for_tx><meas_period><period_unit>.

Some examples in hexadecimal:

“028182”: set the <up_frame_mask> to 0x82 => the next uplink frames will include the <analog_meas> field only

"028604605401" set <nb_meas_for_tx> to 4, <meas_period> to 21600*<period_unit> seconds, <period_unit> to 1 second

== Power consumption ==

Power consumption calculator based on the number of measurements and transmissions.

TBD

NIS-NH3 Gas Sensor - Revision history

Arl: Created page with " NH3 Gas Sensor = General information = {{:NIS Overview}} = Mechanics = * Dimensions 60 x 95 x 85mm (109mm including..."