GSS Sensor User`s Manual
Contents
1. Location Name Purpose Default Value 0 AHHI Reserved 0 1 ANLO Reserved 0 2 ANSOURCE Reserved 0 24 f3CO2Meter com CO2 Measurement Specialists 3 ACINITHI Autocalibration Preload This preloads the 87 autocalibration timer so that the first autocalibration occurs after a shorter time 4 ACINITLO Low byte of above 192 5 ACHI Autocalibration Interval Sets the time interval 94 between autocalibrations 6 ACLO Low byte of above 128 7 ACONOFF Switches Autocalibration ON OFF 0 8 ACPPMHI Autocalibration Background Concentration This 1 determines what background CO level is assumed for autocalibration 9 ACPPMLO Low byte of above 194 10 AMBHI Ambient Concentration for G command This 1 determines what background CO level is assumed for ambient calibration using the G command 11 AMBLO Low byte of above 194 12 BCHI Buffer clear time This will clear any incomplete 0 commands from the serial buffer after a fixed period of inactivity The time is in half second increments 13 BCLO Low byte of above 8 200 231 User EEPROM 255 9 2 4 Autocalibration Settings locations 3 7 These are included now to maintain compatibility with previous firmware versions We recommend using the command to set autocalibration timings 9 2 5 User EEPROM Locations 200 to 231 can be used to store user values Each location is a single byte These locations are not used by the2. 2 3 2 Temperature Measurement Optional The temperature measurement is reported as T r n where is a five digit number To convert to C subtract 1000 and divide by 10 For example T 01235 r n Represents 23 5 C NB The temperature and humidity sensor is a factory fit option If it is not fitted the sensor will return T 01000 f3CO2Meter com CO2 Measurement Specialists 2 3 3 Humidity Measurement Option The humidity measurement is reported as H r n Where is a five digit number To convert to relative humidity 46 divide by 10 For example H 00551 r n Represents 55 1 RH NB The temperature and humidity sensor is a factory fit option If it is not fitted the sensor will return H 00000 2 3 4 Example of T H and CO When shipped the sensor default output is CO2 only To output temperature humidity and CO send M 4164 r n see Output Fields The output format will have the form H 00345 T 01195 Z 00651 r n This example indicates 34 5 RH 19 5 C and 651ppm CO 10 f3CO2Meter com CO2 Measurement Specialists 3 Command Summary For complete details of the commands and their correct usage please refer to the Command Reference IMPORTANT e All commands must be terminated with a carriage return and line feed lt CR gt lt LF gt In this document this is shown as r n e Commands which take a parameter always have a space between the letter and t
3. Altitude compensation applies a permanent correction to the sensor response so should only be used when it is known that the sensor will be operating at altitude permanently NDIR gas sensors such as the COZIR SprintlR and MISIR family of sensors detect the concentration of gas by measuring the degree of light absorption by the gas analysis The degree of light absorption is then converted into a concentration reported by the sensor The absorption process is pressure dependent so that a change in pressure will cause a change in the reported gas concentration As the pressure increases the reported gas concentration also increases As the pressure decreases the reported concentration decreases This effect takes place at a molecular level as is common to all NDIR gas sensors In normal use the reading will vary by 0 196 of reading for each mbar change in barometric pressure the sensor are calibrated at 1013mbar If the sensor is installed at an elevated altitude the mean barometric pressure will be lower than 1013mbar It is possible to configure the sensor to correct for this effect by setting the altitude when installing This will apply a permanent correction to the output of the sensor depending on the altitude setting selected To apply this correction 1 Select the appropriate code from the table below intermediate values can be interpolated 2 Sendthe S r n tothe sensor where is the code from the table be
4. ccccccccccsssssecececesseseseeeeeeescsesaeaeeeeeceseeeaaeeseessesseseaeeeeeesees 37 11 9 Minimizing Power using Command Mode sesenta nnns nnns 38 11 10 Command Mode Power Reduction Key Points 39 11 11 Minimizing Power by Power Cycling eene nnne nenne nennt nnn nnn 40 11 12 Power Cycling Key Points e eb re Enero eode iae ne vius eve ee via eu AVE tate 41 11 13 Implementing a User Auto Calibration Routine nennen nennen nnn 42 12 Appendix B Analog Voltage Output 43 12 1 Ordering Informatio Masner EEEo ETTOR ANEN ENSE NEEE EONA TENE 43 12 2 Voltage Output Connechons eene nennen nnne nnns Ear E E aara tias ases 44 12 3 EE Bloe En Ce i tr terrre eiae va EE erra Fo dede e E edem e d e a ERE 44 12 4 Converting Voltage to Concentration ener nnns nnn nnns sene n nenas nasse 44 12 5 Linearity of the Voltage Output 45 12 6 Noise on the Voltage Output 46 12 7 Changing the Full Scale Concentration esssssessssseesesee eene nnne nnn nnne nter nnns nnns 46 128 Digital OUTPUTS 33 2 0 5 E E 47 12 9 Zero Point CaliDratiOn i aree eoe nete ce itae eo Ed C deh dane ae dte desde e s 47 13 Appendix C Setting the Auto Calibration Parameters for Older Firmware cc ccccccssssssseeeeeeseesees 48 13 1 Environmental Requirements for Auto calibration cccccccccceessesseseeececesseseaeeeeessessessaaeeeeess 48 13 2 Auto calibration using GasLlab EE 48 13 3 Sett
5. T 1 3 5 7 9 TX 13 325 27 29 21 23 25 27 29 Time minutes 36 f3CO2Meter com CO2 Measurement Specialists 11 7 Minimizing the Power in Streaming and Polling Modes Both polling and streaming are continuous power modes using 3mW 3 5mW The power consumption and measurement cycle cannot be varied in these modes so the user must simply focus on minimizing any options on the sensor The lowest power is achieved by reporting one value only the CO measurement Additional features will increase the power consumption for example temperature and humidity measurement voltage output or additional output fields These should be avoided in low power applications 11 8 Polling and Streaming Key Points Use polling mode to minimize transmission time This will reduce the average power consumption by approximately 0 5mW depending on the polling frequency Ensure that only necessary output fields are turned on to minimize the measurement Tx time Use the M command to configure the output fields To return the filtered CO value only recommended send M 4 r n to the sensor Each additional output field will add approximately 0 25mW to the total power consumption Use the digital output from the sensor only The voltage output optional fit increases the power consumption The temperature and Humidity sensor optional fit increases the power consumption by approximately 1mW The lowest achievable power using continuous measurements
6. Commands 2000ppm COZIR A 7 208 PO7 P 1208 5000ppm COZIR A 19 136 PO19 P1136 10000ppm 196 COZIR A 39 16 P 039 P116 10000ppm 196 COZIR W 3 232 P03 P1232 596 COZIR W 19 136 PO19 P1136 1096 COZIR W 39 16 P039 P116 70 COZIR W 100 27 88 PO27 range P188 Warning If the full scale value is set higher than the sensor range ie the range when first supplied the voltage values will be incorrect and must not be used 12 8 Digital outputs The digital serial Rx and Tx connections are still available and active when the voltage output is fitted This allows the sensor to be calibrated and configured over the serial connections 12 9 Zero Point Calibration The serial communication options are also available The COZIR sensor requires periodic zero point calibration In many cases this can be done automatically using the built in auto calibration option Additionally two zero calibration pins area available Nitrogen Zero Pin 8 This pin is normally high Hold it low for 1 5s to trigger a nitrogen zero This assumes that the sensor is free from any CO2 Ambient Zero Pin 10 This pin is normally high Hold it low for 1 5s to trigger an ambient zero This assumes that the sensor is in fresh air default setting is 450ppm 47 f3CO2Meter com CO2 Measurement Specialists 13 Appendix C Setting the Auto Calibration Parameters for Older Firmware Older COZIR and SprintIR sensor firmware set the auto cali
7. Concentration 44 f ACO2Meter com CO2 Measurement Specialists Vout voltage output at pin 9 Vsupply supply voltage at pin 3 All voltages relative to GND pin 1 Note that there is a slight zero offset see below which should be taken into account for readings below 1096 of the Full Scale 12 5 Linearity of the Voltage Output Figure 2 shows a typical plot of output voltage at pin 9 vs CO2 concentration e Note that the output voltage is linearly dependent on the CO concentration measured by the sensor e Note also that for CO2 concentrations less than 10 of full scale the sensor output voltage is affected by the output Operation Amplifier offset voltage 14mV See below Output Linearity This graph assumes a supply voltage of 3 3V Analogue Voltage output in Volts 0 Percentage of sensor CO2 ppm range Effect of zero offset close to 0 This graph assumes a supply voltage of 3 3V Analogue Voltage output in 0 5 10 Percentage of sensor CO2 ppm range 45 f3CO2Meter com CO2 Measurement Specialists 12 6 Noise on the Voltage Output The typical noise present on the voltage output is as follows with the voltage output at half full scale e 140uVrms measured in a 20kHz bandwidth e 450uVrms measured in a 10MHz bandwidth e Ina 10MHz bandwidth the highest noise voltage amplitude is at least 70dB below the desired DC output voltage 12 7 Changing the Full Scale Concen
8. K command see COZIR Software User s Guide for details 11 2 Streaming Mode K 1 This is the factory default Measurements are made and transmitted twice per second for COZIR MISIR and MinIR sensors and 20 times per second for SprintIR sensors To enter Streaming mode send K 1 r n The power consumption is approximately 3 5mW 11 3 Polling Mode K 2 In this mode data is not transmitted until requested however the sensor continues to make measurements twice per second for COZIR MISIR and MinIR sensors and 20 times per second for SprintlR sensors To enter Polling mode send K 2 r n The typical power consumption in this mode is 3 0mW when data is not being polled and 3 5mW when data is polled 11 4 Command Mode K 0 In command mode no measurements are made or reported This mode is primarily intended to be used when interacting with the sensor for example to read the serial number to determine the status or to set output mask or filter values It can be used to reduce the power consumption by reducing the power level when measurements are not required Users looking for the lowest power applications should consider powering down the sensor rather than using command mode to save power To enter command mode send K O r n The typical power consumption in command mode is 1500W 33 f3CO2Meter com CO2 Measurement Specialists 11 5 Current Profile Streaming mode and Polling mode are very similar There is a ver
9. Measurement Specialists 2 Serial Format and Connection 2 1 Connection Communication to and from the various sensors is via a serial connection Pins are shown looking at the connector of the sensor COZIR Ambient GND N C 3 3V N C Rx N C Tx Zero N C Ambient COZIR Wide Range SprintIR 3 z MISIR 00000 00000 e E MinIR GND Ov V 3 3 5 5V 3 3V recommended Tx OUT Voh will be 3V Sensor output Rx IN Used for configuration etc f3CO2Meter com CO2 Measurement Specialists 2 2 Serial Connection The Rx and Tx pins are normally high suitable for direct connection to a UART If the sensor is to be read by a true RS232 device eg a PC it is necessary to pass through a level converter to step up down the voltage and invert the signal Connection to the sensor is via a 10 way 0 1 pitch connector In practice only the first 4 pins are required GND 3V3 Rx and Tx so a 4 way connector can be used A Development kit and free GasLab software is available to allow USB interfacing between COZIR and SprintIR sensors and a PC Contact CO2Meter com for details Parameter Value Baud Rate 9600 Data Bits 8 Parity None Stop Bits 1 Format UART normally high Hardware Flow Control None Voltage Voh 3V MISIR Vor Vsupply Voltage Vih 3V 5V Note If you connect to the sensor using HyperTerminal you must select the box Sen
10. Send a zero set point Syntax ASCII character u SPACE decimal terminated by 0x0d Ox0a CR amp LF Response u 32767 r n NB For advanced use only Contact GSS before using this command There are three variants of the autocalibration configuration command COMMAND 0x40 INFORMATIO Example r n Description Return the autocalibration settings Syntax ASCII character terminated by Ox0d Ox0a CR amp LF Response 1 0 8 0 r n if autocalibration is enabled O r n if autocalibration is disabled 29 f3CO2Meter com CO2 Measurement Specialists COMMAND 0x40 CALIBRATION USE WITH CARE Example O r n Description Switch off the autocalibration function Syntax ASCII character followed by a SPACE followed by a zero terminated by OxOd 0x0a CR amp LF Response e Or COMMAND 0x40 CALIBRATION USE WITH CARE Example 1 0 8 0 Xr An Description Set the Autocalibration timing Syntax See Autocalibration section Response 1 0 8 0 r n the number mirrors the input value 10 5 Polling Commands H COMMAND 0x48 INFORMATIO Example Hirn Description Reports the humidity measurement from the temperature and humidity sensor if fitted Divide by 10 to get the RH Syntax ASCII Character H terminated by OxOd Ox0a CR amp LF Response H 00551 r n T COMMAND 0x54 INFORMATIO Example T r n Description Reports the humidity measurement from the temperature
11. Sensor Noise vs Filter Setting Sensor Noise Filter Setting Increasing the filter setting has a beneficial impact on noise so improves the sensor resolution It also slows the sensor response to transients This can be used to improve the detection of average CO2 conditions In building control for example a fast response to breathing near the sensor is undesirable If the transient response is important either for speed of response or because the shape of the transient is required a low filter setting should be used The following chart shows the same transient event capture using a filter setting of 4 and using a filter setting of 32 22 f3CO2Meter com CO2 Measurement Specialists Effect of Filter on Transient Response Filter 4 Filter 32 Reported CO2 A 9 1 2 Setting the Digital Filter To change the setting type A r n where is the required filter setting For most applications a filter setting of 32 is recommended send A 32 r n response A 00032 r n If the filter is set to zero a smart filter mode will be used in which the filter response is altered to suit the prevailing conditions This is useful if there is a combination of steady state conditions with some periods of rapidly changing concentrations 9 1 3 Reading the Digital Filter Setting The current setting for the digital filter can be determined by send
12. available on COZIR sensors that include RH T or SprintIR sensors All MISIR sensors have a voltage output This operates in the same way as the COZIR voltage output except that the full scale voltage is 3V regardless of the supply voltage 43 TCO2Meter com CO2 Measurement Specialists 12 2 Voltage Output Connections The voltage output is available on pin 9 of the sensor Power and ground must be applied to pins 1 and 3 3V3 3V3 RX TX Voltage O P voltage O P COZIR A Series Connections COZIR W Series Connections 12 3 Load Impedance The COZIR voltage output pin has an internal resistance of approximately 1500 The internal capacitance between the voltage output pin and OV is 220nF This gives the output a single order high frequency roll off at about 4 8kHz To avoid loading issues affecting the measurement it is essential to ensure that load connected to the voltage output pin 9 is greater than 10kQ and preferably greater than 100kQ 12 4 Converting Voltage to Concentration The voltage output is provided by Pulse Width Modulation PWM of the sensor supply voltage This means that all voltage outputs are relative to the supply voltage For example if the supply voltage is 3 4V then the full scale output from the voltage pin will also be 3 4V the half scale voltage will be 1 7V etc To convert a voltage into a CO concentration Concentration FS Vou Vsupply Where FS Full Scale
13. guidelines We have developed these requirements after rigorous testing to maximize the performance and accuracy of the sensor in the host application 1 1 Power Supply The sensors must be powered with a linear regulator for maximum precision Power supplies with high frequency noise such as switching supply circuits can cause increased noise in the sensor s measured value Altering the power supply will require recalibration We recommend calibrating the sensor in its final installation calibrating the sensor outside with a different configuration will yield inconsistent calibration results 1 2 Calibration Procedure We recommend calibrating all sensors The procedure differs between models Calibration gas is available from CO2Meter directly 1 3 Ambient Sensors For ambient sensors we recommend an atmospheric calibration Fresh air is generally assumed to be at 450ppm but alternatively you can use 450ppm calibration gas This reading can be confirmed with 2 000ppm calibration gas to check the span of the sensor although this step is unnecessary 1 4 Wide Range Sensors For wide range sensors we recommend a zero calibration using an end of range 95 gas This reading can be confirmed with other high concentration CO2 calibration gases such as 5096 and 2596 although this step is unnecessary 1 5 Physical Configuration The sensor can be configured with optional tube caps available through our website or simply in an atmosp
14. interface is required to configure the COZIR Even if the end application will use only a voltage interface we recommend that designers use a digital interface eg GSS USB to serial cable when evaluating the sensor The voltage output is for CO measurement only Temperature and humidity outputs optional are only available as digital UART outputs The COZIR range of sensors can be fitted with an optional voltage output in addition to the standard digital UART output This is available to facilitate interfacing to legacy systems which can only handle a voltage input GSS recommends that a digital sensor is used wherever possible The voltage output is proportional to the CO2 concentration Key points to note are The maximum voltage output full scale will always be that applied to pin 3 of the 10 way connector Care must be exercised in selecting the load resistance connected between the voltage output pin 9 and GND pin 1 The voltage output pin pin 9 is an output pin only Take care not to feed any voltage current into the voltage output pin The voltage output is a factory fit option It is not present unless requested The supply voltage should be 3 3V 0 1V The sensor will continue to operate up to 5V however the voltage output is valid only when the supply is in the range 3 2V to 3 4V 12 1 Ordering Information The voltage output is default for reading CO2 levels on COZIR sensors without RH T It is not
15. sensor E g to store the number 42 in the first user EEPROM location send P 200 42 r n response P 00200 00042 r n and to read it send p 200 r n response p 00200 00042 r n Note that the EEPROM is only guaranteed for 100 000 write cycles 25 f3CcOo2Meter com CO2 Measurement Specialists 10 Command Reference This gives the complete command set for the COZIR SprintlR and MISIR sensors and illustrates use of some of the more commonly used options Key points to note are e In all cases commands are terminated with a carriage return line feed n e Commands are case sensitive e The commands use all use ASCII characters Each command lists the ASCII letter and includes the hex code for avoidance of doubt e Always check for a correct response before sending another command e fa command is unrecognized the sensor will respond with a WARNING This document is provided to give a complete reference of the command set and outputs from the COZIR sensor It is intended for advanced users only If in doubt please contact CO2Meter com prior to use 10 1 Customization A COMMAND 0x41 USER CONFIGURATION Example A 128 r n Description Set the value for the digital filter Syntax ASCII character A SPACE decimal terminated by 0x0d 0x0a CR amp LF Response A 00032 r n a COMMAND 0x61 INFORMATION Example a r n Description Return the value for the digital filter Syntax ASCII C
16. 2 typically nitrogen and allow time for the sensor temperature to stabilize and for the gas to be fully diffused into the sensor Send the command Ur Yn The sensor will respond with an echo of the command and the new zero point For example send U r n response U 32950 r n 6 3 Zero in Fresh Air assumed to be 400ppm If there is no calibration gas and no nitrogen available the sensor zero point can be set in fresh air The sensor is programmed to assume that fresh air is 400ppm this value is user configurable see User Settings 15 f3CO2Meter com CO2 Measurement Specialists Place the sensor in a fresh air environment and allow time for the sensor temperature to stabilize and for the fresh air to be fully diffused into the sensor Send the command Gr Vn The sensor will respond with an echo of the command and the new zero point For example send Gir An response G 32950 r n 6 4 Fine Tune the Zero Point If the CO2 concentration and the sensor reported concentration are known the zero point can be adjusted using the known concentration to fine tune the zero point This is similar in operation to the X command see above but can operate on historic data For example if the sensor has been in an environment in which it is known to have been exposed to outside air and the sensor reading is known at that time the zero point can be fine tuned to correct the reading This is typically used to implement automate
17. E sten tenes Aaa a 13 4 2 Mode 1 Streaming Mode nennen nennen nnn nnnn nass sensit anien asiste tias sanis 13 4 3 Mode 2 Polling Mode ree rre tee rh aee v ese rra YR E E 13 OUTPUT FIG AS verdes 14 Zero Point Calibr tiOn 2e R tete to gea eee te dete a oet dea dee Feed aea va EORR LAKE etu ee Dg s 15 6 1 Zero in a Known Gas Concentration recommended sess 15 6 2 e tal NIOEN ET RICE DD DD DU DD LEE 15 6 3 Zero in Fresh Air assumed to be A Oppm enne enhn nnne nhn nne ni nas 15 6 4 Fine Tune the Zero Point 2 rete agelaut i aan FER Run rada Nea Ed da Ra ERE Ra Mae Niel 16 6 5 Zero Point Adlustment RRRRERREEEMEEEEEMEEEEEMMEEEEMMEEMMMM 16 A toCalibratiOrt ducis cetur idee ed N edet tana Qe aser eei eu neta Pedo eed dea eed RR T 16 7 1 Principle Re EE 16 7 2 Requirements for AUtO Calibration eene nennen nennt nnne nent na nnne nana 17 7 3 Setting the Auto Calibration Parameters ener enne nnns nennen nnns 17 7 4 Autocalibration Intervals eene en nens en tense en ness nensi nnns 18 7 5 Read the Autocalibration Settings sessi enne nnne nnn nnn nass nna 19 7 6 Disable Autocalibration En 19 7 7 Background Concentration ccccccessscccceescsecssaeeececsesesneeeeeeeceseeseeaeeeeeesseeesasaeeeseeesseseaeaeeesensees 19 Altitude Compensation cecene ttan ENEE 20 Eigen ecu eet geet EE Eeer ER 9 1 IRSCH ER 9 1 1 Customizing the Se
18. GSS Sensor User s Manual bet COZIR SprintIR MISIR and MinIR Sensors August 2015 Rev O2Meter com CO2 Measurement Specialists 131 Business Center Drive Ormond Beach FL 32174 386 872 765 Sales 386 256 4910 Support www CO2Meter com Sales CO2Meter com 1 f3CO2Meter com CO2 Measurement Specialists Table of Contents Guidelines for All Sensors RM 5 1 1 POWEr SUP mp 5 1 2 Calibration Proced re EE 5 1 3 tele 5 1 4 Wide Range Sensors ccscccccccecsssssseecececeesesneaecececeseeuaeeececsceesesseaeeeseeseesaeaeeeesesseesuaaaeeeesseesesaaaeeeeess 5 1 5 Physical Configuration c ccccccccccssssssecececessessaececececeseeaeeeeeescesecsesaeseeessseseaaeaeeeesseseesaeeeseeessesesaeas 5 1 6 Dynamic Power Requirements eese eene nennen nnne n nnns nsns sss s asse nsns esses essen ener nnn 6 Serial Format and Connection EE 7 2 1 Connection EE 7 2 2 Serial elle te EE Pre dria eat c EE 8 2 3 ee E E 8 2 3 1 COs Measurement sssini aaa ERR IS E ERR ERRE RENE EES eis 8 2 3 2 Temperature Measurement Optional 9 2 3 3 Humidity Measurement Option 10 2 3 4 Example of T H and CO 10 Command Summary ccccccceceseesesseceececeesesaaececeesceeseaeaeeececesseseaaeseeesssesesaeaeeeeecsseeesaaeeeesceeseaaaesesesecesaes 11 Operating MORS pisent inna oa Fou rette dei teen oteberesse rat Veteran ite setae sedg 13 4 1 Mode 0 Command Mode sess esee eene enne EAREN A
19. ON USE WITH CARE Example G r n Description Calibrates the zero point assuming the sensor is in 400ppm CO Syntax ASCII character G Response G 33000 r n the number is variable F COMMAND 0x46 CALIBRATION USE WITH CARE Example F 410 390 r n Description Calibrates the zero point using a known reading and known CO2 concentration Syntax ASCII character F then a space then the reported gas concentration then a space then the actual gas concentration Response F 33000 r n the numbers are variable 28 f3CO2Meter com CO2 Measurement Specialists X COMMAND 0x58 CALIBRATION USE WITH CARE Example X 1000 r n Description Calibrates the zero point with the sensor in a known concentration ofCO Syntax ASCII character X then a space then the gas concentration Response X 33000 r n the number is variable S COMMAND 0x53 CALIBRATION USE WITH CARE Example S 8192 r n Description Set the Altitude Compensation value in EEPROM Syntax ASCII character S SPACE decimal terminated by 0x0d 0x0a CR amp LF Response S 8192 r n the number mirrors the input value s COMMAND 0x73 INFORMATIO Example s r n Description Reports the Altitude Compensation value in EEPROM See Altitude Compensation Syntax ASCII Character s terminated by OxOd 0x0a CR amp LF Response s 8193 r n u COMMAND 0x75 USE ONLY WITH CO2Meter com GUIDANC Example u 32767 r n Description
20. ace between the first letter and any parameter For example the X command reads X space 2000 carriage return line feed Note that all settings are stored in non volatile memory so the sensor only has to be configured once It should not be configured every time it is powered up 12 f3CO2Meter com CO2 Measurement Specialists 4 Operating Modes The COZIR SprintIR MISIR and MinIR sensors can be operated in three different modes Users can switch between the modes using the K command 4 1 ModeO Command Mode This is primarily intended for use when extracting larger chunks of information from the sensor for example using the Y and commands In this mode the sensor is stopped waiting for commands No measurements are made and the sensor will run through a warm up cycle after exiting this command There is no latency in command responses The power consumption is less than 3 5mW as no measurement activity takes place Commands which report measurements or alter the zero point setting are disabled in mode O Mode 0 is NOT retained after power cycling The sensor will always power up in streaming or polling mode whichever was the most recently used 4 2 Mode1 Streaming Mode This is the factory default Measurements are reported twice per second for COZIR MinIR and MSIR sensors and 20 times per second for SprintIR sensors Commands are processed when received except during measurement activity so there may be a t
21. alists 7 5 Readthe Autocalibration Settings To determine the current autocalibration settings send Q r n response 8 1 0 8 0 r n If the autocalibration is enabled the sensor will respond with the format above showing the initial and regular autocalibration intervals If the autocalibration is disabled the sensor will respond with send Q r n response O r n 7 6 Disable Autocalibration To disable the autocalibration send O r n response O r n ie followed by a space followed by a zero terminated with OxOd OxOa 7 7 Background Concentration The background concentration depends somewhat on the area the sensor is installed Typically a figure between 400ppm and 450ppm is used The factory default is 400ppm To set this send P 8 xir An P 9 y r n where x and y depend on the concentration you want to set Concentration X Y 380 1 124 400 1 144 425 1 169 450 1 194 This is stored as a two byte value the high byte being in location 8 and the low byte in location 9 The value represents the concentration 19 f3CcOo2Meter com CO2 Measurement Specialists To calculate other values x int concentration 256 y the remainder after dividing concentration 256 8 Altitude Compensation Important This feature was introduced in sensors manufactured after July 2013 using firmware version AL17 or higher The firmware version can be identified by sending the Y or command
22. and humidity sensor if fitted Subtract 1000 and divide by 10 to get the temperature in C Syntax ASCII Character T terminated by OxOd Ox0a CR amp LF Response T 01224 r n Z COMMAND 0x5A INFORMATIO Example Z r n Description Reports the latest CO2 measurement in ppm Syntax ASCII Character Z terminated by OxOd Ox0a CR amp LF Response Z 00512 r n 30 f3CO2Meter com CO2 Measurement Specialists Q COMMAND 0x51 INFORMATIO Example Qirin Description Reports the latest measurement fields as defined by the most recent M command Syntax ASCII Character Q terminated by OxOd Ox0a CR amp LF Response H 12345 T 12345 Z 00010 r n 31 f3CO2Meter com CO2 Measurement Specialists 11 Appendix A Power Consumption The COZIR family of sensors offers low power CO2 sensing using patented GSS sensor technology COZIR sensors are available over the whole measurement range from 400ppm to 10096 COZIR sensors have been optimized for use in battery power applications where the short startup time and low power consumption offer very significant advantages over standard NDIR sensing technology Because of the very rapid power up time COZIR sensors are also being used in energy scavenged applications using power sources such as PV cells where it is essential to minimize the energy used per measurement This document considers the best methods to use in applications where energy is limited There a
23. be long enough to allow the filter response to reach a final value The required warm up time in seconds is approximately equal to the filter value Filter Setting Warm up Time 1 1 2s 2 3s 4 5s 8 9s 16 16s 32 32s The graph shows a typical start up from command mode or from power up there is no difference In this case the digital filter value was 8 In this case the digital filter setting was 8 Warm up Digitally Filtered Raw Measurement 600 amp 500 ee Ae AA lie fh ADA NN 400 av 300 2 a 200 iN 100 0 S 0 5 10 15 20 25 30 35 40 c Time after Power Up The choice of filter setting is a trade off between reducing noise and reducing power higher filter lower noise lower filter shorter warm up 35 ACO2Meter com CO2 Measurement Specialists These shows the same sensor data but with filter settings of 1 4 and 8 and the corresponding warm up period The figure graphed is the CO reading reported by the sensor at the end of the warm up period C02 Measurement ppm 800 750 700 650 600 550 500 Power Cycle 1 2s on 60s off 1 3 5 7 9 132 23 35 G 39 21 23 25 27 29 Time minutes C02 Measurement ppm 800 750 700 650 600 550 500 Power Cycle 5s on 60s off T T T T T T T 1 3 5 7 9 41 313 215 EE 19 21 23 25 27 29 Time minutes C02 Measurement ppm 800 750 700 650 600 550 500 Power Cycle 10s on 60s off
24. bration parameters directly into the EPROM memory locations 3 7 using the P and p commands These are included now to maintain compatibility with previous firmware versions We recommend using the command instead of the P command to set auto calibration timings 13 1 Environmental Requirements for Auto calibration Exposure to Fresh Air The sensor must see fresh air at least once during the auto calibration period You do not need to know when the fresh air will be sensed just that it will be sensed at some point during the period Continuously Powered The auto calibration information is deleted when the sensor is switched off This ensures that each installation is unaffected by any previous history of the sensor For auto calibration to function it must be power on for the whole of the auto calibration period 13 2 Auto calibration using GasLab The simplest way to set up a sensor for auto calibration is to use the Gaslab software You can download GasLab here http www co2meter com pages downloads The next sections show how to set up the auto calibration using Hyper Terminal or your own software 13 3 Setting the Auto Calibration Parameters Three parameters are required to enable the auto calibration routine Auto calibration period This determines how often the auto calibration takes place Background Concentration Typically 400 450ppm This is the level the sensor will use as background Initial Auto calibration Perio
25. ch defines the output fields The mask value is created by adding the mask values for the parameters required see table below The sensor will output a maximum of five fields If the mask setting represents more than five fields only the first five those with the highest mask values will be output SprintIR sensors have a limited time to transmit information so no more than two fields should be selected for output Parameter Field Mask Comments Identifier Value Humidity H 4096 Reports the humidity output of the Temperature and Humidity Sensor if Fitted D digitally filtered d 2048 Reports a value related to the normalized LED signal strength smoothed D unfiltered D 1024 Reports a value related to the normalized LED signal strength Zero Set Point h 256 Reports a value related to the normalized LED signal strength Sensor Temperature V 128 Reports a value which varies inversely with the sensor unfiltered temperature Temperature T 64 Reports the temperature output of the Temperature and Humidity Sensor if Fitted LED Signal digitally o ER Reports a value which gives an indication of the LED signal filtered strength smoothed LED Signal unfiltered O 16 Reports a value which gives an indication of the LED signal strength Sensor Temperature v 8 Reports a value which varies inversely with the sensor filtered temperature smoothed CO2 Output Digitally Z 4 Digitally fil
26. ch font is used to show commands sent to the sensor and transmissions received from the sensor RoHS Certification GSS Ltd hereby certifies that the COZIR SprintlR and MISIR products are RoHS compliant and fulfils the definitions and restrictions defined under Directive 2011 65 EU of The European Parliament and of the Council of June 8 2011 on the restriction of the use of certain hazardous substances in electrical and electronic equipment EEE RFI amp CE Certification The COZIR family of sensors has been used in client and GSS products which have successfully passed through full CE certification This includes radiated noise immunity as per EN61000 4 3 2006 Type 1 80 1000MHz 3V m 80 1kHz AM 1400 2000 3V m 80 1kHz AM 2000 2700MHz 1V m 80 1kHz AM To minimise issues with noise immunity we recommend the following e Adda decoupling capacitor across the supply close to the sensor e Ifyou are using a switched mode supply use shielded inductors and locate away from the sensor This also applies to other magnetic components such as electromagnetic buzzers e Always adhere to the respective manufacturer s advice on PCB layout for switched mode power supply devices e Avoid routing power tracks or leads across the sensor f3CO2Meter com CO2 Measurement Specialists 1 Guidelines for All Sensors To achieve maximum precision when integrating the GSS line of sensors into a product we recommend following these
27. d It is possible for the first auto calibration to take place more quickly than the regular auto calibration event This can be useful to stabilize quickly after installation Before setting the auto calibration parameters please note the following e Before altering the auto calibration parameters switch the sensor into command mode send K 0 lt CR gt lt LF gt This stops the measurement process in the sensor 48 f3CO2Meter com CO2 Measurement Specialists e All commands must be terminated with r n carriage return line feed NB HyperTerminal does not add the line feed character as standard The ASCII Setup must be configured to append line feeds e For details on the commands used please consult the COZIR Software Interface Guide e Foran example of a typical setting see Auto calibration Example 13 4 Background Concentration The background concentration depends somewhat on the area the sensor is installed Typically a figure between 400ppm and 450ppm is used To set this send P8x r n P 9 y r n where x and y depend on the concentration you want to set Concentration X Y 380 1 124 400 1 144 425 1 169 450 1 194 This is stored as a two byte value the high byte being in location 8 and the low byte in location 9 The value represents the concentration To calculate other values x int concentration 256 y the remainder after dividing concentration 256 13 5 Auto calibrati
28. d calibration routines The command takes two parameters separated by a space The first parameter is the reading reported by the sensor The second is the corrected reading Both parameters must be in the same units as the sensor output see Reading Format The sensor will respond with an echo of the command and the new zero point For example send F 400 380 r n response F 32950 r n In this example the sensor zero point would be corrected so that a reading of 400ppm would now be reported as 380ppm 6 5 Zero Point Adjustment The precise zero point can be fine tuned by sending a zero point to the sensor This is not recommended for general use Send the command u r n where is the new zero point 7 AutoCalibration 7 1 Principle of Operation COZIR sensors are fully calibrated prior to shipping from the factory Over time the zero point of the sensor needs to be calibrated to maintain the long term stability of the sensor In many applications this can happen automatically using the built in auto calibration function 16 f3CO2Meter com CO2 Measurement Specialists This technique can be used in situations in which sensors will be exposed to typical background levels 400 450ppm at least once during the auto calibration period For example many buildings will drop quickly to background CO levels when unoccupied overnight or at weekends The auto calibration function uses the information gathered at the
29. d in auto cal counts where a count is 50s To disable set the initial auto cal period to 0 This is stored as a two byte value the high byte being in location 5 and the low byte in location 6 The value represents the number of counts between auto calibration events where each count lasts 50 seconds f3CO2Meter com CO2 Measurement Specialists 13 7 Auto Calibration Examples This give two example of typical auto calibration settings Example 1 To set auto calibration to take place every week with the first auto calibration event taking place 36 hours after power up The background level is assumed to be 450ppm KO P70 P337 P 432 P547 P664 P81 P 9 194 P71 Then switch the sensor off for 30 seconds and on again Example 2 To set auto calibration to take place every 3 weeks with no initial auto calibration The background is assumed to be 420ppm KO P70 P30 P40 P5141 P6191 P81 P 9 164 P71 Then switch the sensor off for 30 seconds and on again 51
30. d line ends with line feeds under ASCII setup When initially powered the sensor will immediately start to transmit readings see Mode 1 in Operating Modes 2 3 Reading Format 2 3 1 CO Measurement The CO measurement is reported as Z HHHEz HE TM where Z shows the CO concentration after digitally filtering and z shows the instantaneous CO concentration without any digital filtering f3CcO2Meter com CO2 Measurement Specialists The concentration is reported in the following units Type Range Units Example COZIR A Up to 296 ppm Z 00631 631ppm MISIR COZIR W Up to 6596 ppm 10 Z 01200 12000ppm 1 2 SprintIR W MinIR 5 COZIR W 100 Up to 100 ppm 100 Z 01500 150000ppm 15 SprintIR W 100 MinIR 100 Note that the same units must be used when sending concentration information to the sensor for example the X command and the F command If in doubt the Command see below will indicate what multiplier should be applied to the Z output to convert to ppm Z 00842 z 00765 Sample output from a sensor with factory Z 00842 z 00738 settings Z 00842 z 00875 00858 This is a COZIR A so the reported CO reading Z 0084 S is 842ppm Z 0084 Z 0084 0084 0084 unfiltered CO reading Z Z D z 0084 See Digital Filter for more details Z 0084 The second figure shows the instantaneous Note that all output from the sensor has a leading space
31. efinitely from a solar cell or for many years from a small primary cell The user must address zero point calibration autocalibration see below The typical implementation is Select polling mode and set filter to appropriate value Power On the sensor wait d seconds send Z r n response Z 00610 r n eg Power off the sensor Wait n seconds Power on the sensor Wait for the warm up period Request the CO2 reading Power off the sensor Wait until the next reading is required 40 f3CO2Meter com CO2 Measurement Specialists 11 12 Power Cycling Key Points e Ensure that the sensor is configured for polling mode e Ensure that the filter setting matches the planned power on period e COZIR sensors will store configuration information in non volatile memory so this does not need to be refreshed when the sensor is powered up e Oneach power up the sensor must run through the same warm up period See the warm up section for details and recommended times e The autocalibration is disabled when the sensor is powered down and the autocalibration timers are reset on power up Users must implement their own autocalibration routine when power cycling See Implementing a User Autocalibration Routine e The power level will depend on the duty cycle of the sensor e The power switch to the sensor must ensure that the sensor power supply requirements can be met in particular the peak current requirement 33
32. haracter a terminated by 0x0d Ox0a CR amp LF Response a 00032 r n M COMMAND 0x4D USER CONFIGURATION Example M 212 r n Description Determines which values are going to be returned by the unit Syntax M SPACE followed by an up to 5 digit number each bit of which dictates which item will be returned by the sensor terminated by Ox0d Ox0a CR amp LF Response M 212 r n see Output Fields for details 26 f3CO2Meter com CO2 Measurement Specialists P COMMAND 0x50 USER CONFIGURATION Example P 10 1 r n Description Sets a user configurable parameter Syntax P SPACE followed by an up to 2 digit number SPACE followed by an up to 3 digit number terminated by 0xOd Ox0a CR amp LF Response P 00001 00010 r n see User Settings for details p COMMAND 0x70 USER CONFIGURATION Example p 10 r n Description Returns a user configurable parameter Syntax P SPACE followed by an up to 2 digit number terminated by Ox0d 0x0a CR amp LF Response P 10 1 r n see User Settings for details 10 2 Information Y COMMAND 0x59 INFORMATIO Example Y r n Description the present version string for the firmware Syntax ASCII character Y terminated by OxOd Ox0a CR amp LF Response Y Jan 30 2013 10 45 03 AL17 r n B 00233 00000 r n NB This command returns two lines split by a carriage return line feed and terminated by a carriage return line feed This command requires t
33. hat the sensor has been stopped see K command COMMAND 0x59 INFORMATIO Example r n Description Returns anumber of fields of information giving information about the sensor configuration and behavior Syntax ASCII character terminated by OxOd Ox0a CR amp LF Response Contact GSS for details COMMAND 0x2E INFORMATIO Example r n Description Returns a number indicating what multiplier must be applied to the Z or z output to convert it into ppm 27 f3CO2Meter com CO2 Measurement Specialists Syntax ASCII character terminated by Ox0d Ox0a CR amp LF Response 00001 r n this number is variable 10 3 Switching between Modes For discussion of different modes of operation see the section Operating Modes K COMMAND 0x4B USER CONFIGURATION Example K 1 Description Switches the sensor between the operating modes Syntax ASCII character K SPACE followed by the mode number terminated by OxOd 0x0a CR amp LF Response K 1 r n the number mirrors the input value 10 4 Zeroing and Calibration See examples of each of the zero and calibration commands in the following section U COMMAND 0x55 CALIBRATION USE WITH CARE Example U r n Description Calibrates the zero point assuming the sensor is in Oppm CO Syntax ASCII Character U terminated by 0x0d Ox0a CR amp LF Response U 32767 r n the number is variable G COMMAND 0x47 CALIBRATI
34. he parameter e The sensor will respond with a if a command is not recognized The two most common causes are missing spaces or missing lt CR gt lt LF gt terminators Command Use Example Response Comments A r n Set the digital Filter A16 r n A 00016 r n See User Settings a r n Return the digital a r n a 00016 r n See User Settings filter setting F HHH HHHHH r n Fine Tune the zero F 410 400 r n F 33000 r n See Zero Point Calibration point G r n Zero point G r n G 33000 r n See Zero Point Calibration calibration using fresh air H r n Return most recent H r n H 00552 r n 55 2 in the example humidity Humidity sensing is a factory measurement fit option K r n Selects the K 1 r n K 00001 r n See Operating Modes operating mode M HHHHH r n Sets the output M 6 r n M 00006 r n See Output Fields fields P HHH HHH r n Sets a user P110 r n P 00001 00010 r n See User Settings configurable field in EEPROM p r n Reads a user p 10 r n p 00010 00001 r n See User Settings configurable field from EEPROM Q r n Return most recent Q r n See Command Reference fields S HHHH r n Sets the span S 8192 r n S 08192 r n See Span Calibration calibration value s r n Return the span s r n s 08192 r n See Span Calibration calibration value T r n Return the most T r n T 01225 r n 22 5 C in the example recent temperat
35. heric sampling configuration The configuration must be kept consistent between calibration and installation Calibrating with a different setup will result in inaccurate readings when installed When using a sensor without a tube cap we recommend ensuring turbulence is present across the sensor membrane This can be achieved with a calibration chamber featuring a recirculation fan or constant flow from a fixed flow regulator f3CO2Meter com CO2 Measurement Specialists 1 6 Dynamic Power Requirements Bench tested results for ultra low power sensors powered via USB Dynamic power requirements become important when operating from a USB port where the supply current might be being shared over several ports we recommend using powered USB hubs to avoid these potential power issues or when planning for low power applications like solar power When the power is applied to the sensor initially a higher than normal operating current demand will occur This inrush current and period will relate to the impedance of the power supply and device switching power The measurements below were taken whilst connected to a USB port via a USB to UART bridge cable 3 3 volts streaming poled mode and same interval of measurement on a COZIR sensor e Quiescent 300 uA e Measurement interval 500 mS e Measurement period 20ms e Measurement current 30 mA e RMS operating power 2 uW e Startup inrush current 50 mS 60 mA peaks ACO2Meter com CO2
36. ime delay of up to 100mS in responding to commands The power consumption is 3 5mW assuming one field of information is transmitted and there is no temperature and humidity sensor 4 3 Mode2 Polling Mode In polling mode the sensor only reports readings when requested The measurement cycle continues in the background but the output stream is suppressed The power consumption depends on the frequency of polling but is approximately the same as the streaming mode power consumption Note that the sensor will power up in the mode last used If it was last used in KO mode it will power up in either K1 or K2 mode depending on which was most recently used In Polling Mode measurements can be accessed using the polling commands H L Q T and Z see Command Reference 13 f3CO2Meter com CO2 Measurement Specialists 5 Output Fields The COZIR sensor can be configured to output up to five fields of information Typically the only fields of interest are the CO concentration Temperature if fitted and Humidity if fitted This allows users to customize the output string transmitted by the sensor Up to five values can be transmitted in the string The format is always the same each field is identified by a single character followed by a space followed by the five digit number indicating the value of the parameter The output fields can be set by sending a command of the format M 12345 r nwhere 12345 represents a mask value whi
37. ing aV rin send aVr in response a 00032 r n 9 2 User Options EEPROM Settings Some user settings can be altered in the internal EEPROM These settings can be set by using the parameter setting command P and read using a lower case p There are also 32 bytes of user EEPROM storage available 23 f3CO2Meter com CO2 Measurement Specialists 9 2 1 Setting EEPROM To set an EEPROM location send P r n Where the first parameter is the address and the second is the value Note that two byte values must be set one byte at a time For example to change the default value of the ambient gas concentration used for ambient calibration i e the assumed CO concentration in fresh air to 380ppm send send P 10 1 r n response P 00010 O0001Nr n send P 11 124 r n response P 00011 00124 r n 9 2 2 Reading EEPROM To read a parameter value from an EEPROM location send p r n where tt is the address of the parameter Note that two byte values must be read one byte at a time For example to read the value of the ambient gas concentration used for ambient calibration ie the assumed CO concentration in fresh air send p 10 r n response p 00010 00001 r n send p 1i1 r n response p 00011 00124 r n 9 2 3 EEPROM Settings Most of the EEPROM settings are two byte values indicated by HI and LO in the variable name in the following table We recommend contacting GSS before altering the default values
38. ing the Auto Calibration Parametere 48 13 4 Background Concentration esses eene nnne enne nhnnnn nnne nent aan EE E asas ensis 49 13 5 Auto calibration Interval eene nnns inen sensns nnns en 49 13 6 Initial Auto calibration period 50 13 7 Auto Calibration Examples eene nennen nhnnna nen aaaea ienna gana snas sanis 51 f3CO2Meter com CO2 Measurement Specialists This documentation is provided on an as is basis and no warranty as to its suitability or accuracy for any particular purpose is either made or implied Neither CO2Meter Inc nor Gas Sensing Solutions Ltd will accept any claim for damages howsoever arising as a result of use or failure of this information Your statutory rights are not affected This information is not intended for use in any medical appliance device or system in which the failure of the product might reasonably be expected to result in personal injury This document provides preliminary information that may be subject to change without notice This guide applies to software versions from July 2013 For previous versions please refer to COZIR Software USER s Guide Rev F Conventions In this guide r n Is used to indicate carriage return CR line feed lt LF gt characters OxOd OxOa which are required at the end of each string sent to the sensor and are appended to all transmissions from the sensor A denotes an ambient model sensor W denotes a wide range sensor Z 12345 r n Courier fixed pit
39. is approximately 3mW All functionality is preserved and the sensor will be fully responsive to commands at all times 37 f3CO2Meter com CO2 Measurement Specialists 11 9 Minimizing Power using Command Mode It is possible to reduce the power consumption by switching the sensor into command mode between measurements The power consumption in command mode is only 150uW much lower than either polling or streaming data This is simple to implement using the COZIR commands send K 2 r n response K 00002 r n Switch to polling mode wait d seconds Wait for the warm up period send Z r n response Z 00610 r n eg Request the CO2 reading send K O r n response K 00000 r n Switch to command mode Wait until the next wait n seconds reading is required where d isthe warm up delay and n d is the gap between measurements This method offers much lower average power than conventional power up modes though with some loss of functionality 38 f3CO2Meter com CO2 Measurement Specialists 11 10 Command Mode Power Reduction Key Points When exiting from command mode the sensor must run through the same warm up period as a newly powered sensor See the warm up section for details and recommended times None of the zeroing functions are operational in command mode The autocalibration process is timed by measurement cycles As measurement cycles are suspended in command mode the auto calibration period m
40. low For example to correct the sensor for permanent installation at 305m elevation send S 8494 r n response S 08494 r n 20 f3CO2Meter com CO2 Measurement Specialists Altitude ft Altitude m Barometric Pressure mbar Code 1000 305 1050 7889 0 0 1013 8192 1000 305 976 8495 2000 610 942 8774 3000 915 908 9052 4000 1219 875 9322 5000 1524 843 9585 The current setting can be determined by sending a lower case s send s r n response s 08494 r n 21 f3CO2Meter com CO2 Measurement Specialists 9 User Settings 9 1 Digital Filter 9 1 1 Customizing the Sensor Response The CO2 measurement is passed through a digital filter to condition the signal The characteristics of the filter can be altered by the user to tune the sensor performance to specific applications The filter operates as a low pass filter increasing the filter parameter reduces measurement noise but slows the response There is a tradeoff between noise resolution and speed of response The filter can be set to a value between 1 and 65535 Settings larger than 64 are not recommended for normal use A low value will result in the fastest response to changes in gas concentration a high value will result in a slower response Note that the response is also determined by the diffusion rate into the sensor The default setting is 32 This chart shows the effect of changing the filter setting
41. ls Finally send a correction to the sensor to instruct it that this level should be corrected to read the background CO level This uses the COZIR F command This command has the format F r n Where is the reading displayed by the sensor and is the corrected reading For example if the lowest reading measured over 3 weeks was 415ppm and the user wants to correct that to read 400ppm the command would be F 415 400 r n Note that this command can only be used once on a set of historic readings To repeat the F command a new set of readings must be generated Notes 1 Power measurements are typical values for sensors measured at GSS at room temperature Unless otherwise stated power levels assume that each measurement comprises a CO measurement only The optional humidity sensor and voltage output will increase the power consumption The power consumption will increase with temperature Throughout this document r n is used to signify the ASCII characters Carriage Return and Line feed OxOd Ox0a 3 Power levels in command mode vary with temperature This is due to increased current in some of the individual components The power level at 50 C can be 2x the power level at 20 C 42 f3CO2Meter com CO2 Measurement Specialists 12 Appendix B Analog Voltage Output Before selecting the voltage output please consider The voltage output is derived from the digital output it is a PWM driven A digital
42. mA and minimum voltage 3 2V 41 f3CO2Meter com CO2 Measurement Specialists 11 13 Implementing a User Auto Calibration Routine COZIR sensors have an autocalibration feature which uses background tracking to provide long term stability for the sensor This feature is disabled when the sensor is power cycled or switched to command mode and the responsibility for this routine switches to the user It is possible to calibrate the sensor using the standard zeroing commands In many cases it is preferable to implement a version of autocalibration which recalibrates the sensor zero point using the CO background of approximately 400ppm to recalibrate the sensor zero point This relies on the sensor being exposed to fresh air at least once during the calibration interval For many applications this condition is met overnight or during weekends when buildings are little occupied The COZIR sensor has a zero calibration option designed to allow users to implement an autocalibration routine when the sensor is not continuously powered First select a calibration period The choice of period should be long enough to ensure exposure to fresh air so should usually be no less than one week Next select the value of background CO expected COZIR sensors have a default of 400ppm but users can select any value Now review the sensor output during the calibration period and note the lowest CO value recorded This is assumed to be ambient leve
43. nsor RESPONSE eene nennen nh nnna nsns n tras nsa sena an 22 9 1 2 Setting the Digital Filter oer e reed eee ee eae ee dE 23 9 1 3 Reading the Digital Filter Setting useesseeseseseeeeeeeenenene eene nennen enne nnne 23 9 2 User Options EEPROM Setting 23 9 2 1 Setting EEPRON ege g eegente ENNEN 24 f3CO2Meter com CO2 Measurement Specialists 9 2 2 Reading dzuduehe 24 9 2 3 Jig iehuThtcmebeeE I 24 9 2 4 Autocalibration Settings locations 3 7 esses enne enne nnne 25 9 2 5 User diui 25 10 Command ETC 26 dou MEeTcnirpciueebt UE 26 10 2 ah tele E EE ER 10 3 Switching between Modes sese enne neni ni nasse nne ti agas assis sinet a sans sonia 28 10 4 Zeroing and CalibratiO EE 28 10 5 Polling Commands eene eene ette ten ie davades cir rea tee eter EENS 30 11 Appendix A Power Consumption ccccccccccscessssceeececeseesesaeeeceessesesaeaeeeeeceseeseseseeeessessesaaaeseeeessesnaaas 32 11 1 Operating Modes Power Level 33 12 Streaming Mode K 1 ite ice er CE ER EIER V ERE FEN ER ER AEN 33 11 3 Polling Mode K 2 ease eege hee VERE UM Ee ve 33 114 Command Mode K 0 ice iicet et RE ease ER ERE RH ERE S ERE IVA FU ERE TE RAE NER eed 33 P MEET ddidi ce E aiii A EE ANEA EEEE RAS A ESS 34 11 6 Warm up TIME EE 35 11 7 Minimizing the Power in Streaming and Polling Mode 37 11 8 Polling and Streaming Key Points
44. on Interval To set the auto calibration interval send P 5 x r n P 6 y r n where x and y depend on the auto calibration interval you want to set Interval X y 1 week 47 64 2 weeks 94 128 3 weeks 141 192 49 f3CO2Meter com CO2 Measurement Specialists This is stored as a two byte value the high byte being in location 5 and the low byte in location 6 The value represents the number of counts between auto calibration events where each count lasts 50 seconds To calculate other values a auto calibration period in days 1728 x int a 256 y the remainder after dividing a 256 13 6 Initial Auto calibration period To set the initial auto calibration period P 3 x r n P 4 y r n If the first auto calibration event is to occur at the regular auto calibration period set both x and y to 0 Otherwise x and y must be calculated using the desired initial auto calibration time and the regular auto calibration period If the first auto calibration event is to occur at the regular auto calibration period set both x and y to 0 Otherwise calculate as follows a auto calibration period in days b initial auto calibration period in hours c a 24 b 72 x int c 256 y the remainder after dividing c 256 The Initial auto cal period works by preloading the auto cal period count So the value stored is the auto calibration period minus the initial auto cal period Both are measure
45. re three distinct ways to operate the sensor Continuous Power Continuous Measurement 3mW 3 5mW COZIR sensors are designed for continuous power operation The typical power consumption is 3mW in polling mode and 3 5mW in streaming mode In these modes the sensor is constantly measuring two fresh measurements per second COZIR MSIR MinIR or 20 times per second SprintIR In streaming mode all measurements are transmitted In polling mode measurements are only transmitted when requested Continuous Power Interrupted Measurement power depends on usage Switching to a low power command mode 150uw between measurements greatly reduces the average power consumption though with some loss of functionality Power Cycled Operations power depends on usage Short startup allows power cycling which gives the lowest power consumption There is some loss of functionality which must be addressed by the user Operation Measurements Power Autocalibration Consumption Available Streaming 2 20 per sec 3 5mW Yes Polling 2 20 per sec 3 0mW Yes Command Mode on demand 270W Yes but with modification Power Cycling on demand 120uW User Routine Power consumption based on 1 reading every 5 minutes sensor powered for 10s per reading 32 f3CO2Meter com CO2 Measurement Specialists 11 1 Operating Modes Power Levels There are three operating modes available in the COZIR range of sensors Users can switch between modes using the
46. se periods to recalibrate This recording from a sensor shows a typical one week recording in an office environment The auto calibration function uses the low point circled and uses it to recalibrate the zero point 7 2 Requirements for Auto calibration Exposure to Fresh Air The sensor must see fresh air at least once during the auto calibration period You do not need to know when the fresh air will be sensed just that it will be sensed at some point during the period Continuously Powered The auto calibration information is deleted when the sensor is switched off This ensures that each installation is unaffected by any previous history of the sensor For auto calibration to function it must be power on for the whole of the auto calibration period 7 3 Setting the Auto Calibration Parameters Three parameters are required to enable the auto calibration routine Auto Calibration Interval This determines how often the auto calibration takes place Background Concentration 17 f3CO2Meter com CO2 Measurement Specialists Typically 400 450ppm This is the level the sensor will use as background Initial Auto calibration Interval It is possible for the first auto calibration to take place more quickly than the regular auto calibration event This can be useful to stabilize quickly after installation Note that the autocalibration timers are reset when the power to the sensor is interrupted On power on the sensor will al
47. tered CO2 reading Filtered CO2 Output not z 2 Instantaneous CO2 reading filtered Note that most fields are for advanced use only and require specific guidance from GSS engineering for their correct interpretation and use Measurement field are indicated in bold 14 f3CO2Meter com CO2 Measurement Specialists For example to output the temperature humidity and CO2 measurements send M 4164 r n The output string will then be H 12345 T 12345 Z 00010 r n 6 Zero Point Calibration There are a several methods to calibrate the zero point of the sensor The recommended method is zero point calibration in a known gas see X command which will give the most accurate zero setting In all cases the best zero is obtained when the gas concentration is stable and the sensor is at a stabilized temperature 6 1 Zeroina Known Gas Concentration recommended Place the sensor in a known gas concentration and allow time for the sensor temperature to stabilize and for the gas to be fully diffused into the sensor Send the command X r n The concentration must be in the same units as the sensor output see Reading Format The sensor will respond with an echo of the command and the new zero point For example to set the zero point in a COZIR A when the sensor is in a known gas concentration of 2000ppm send X 2000 r n response X 32950 r n 6 2 Zero in Nitrogen Place the sensor in a gas containing no CO
48. tration The full scale concentration of the sensor can be changed via some user settings Note that the full scale concentration must be equal to or lower than the sensor range For example the scaling of a 596 sensor can be changed so that the voltage full scale represents 496 or 196 This must be set using the digital UART interface to the sensor using the P command to set the values in the Sensor EEPROM This is stored in non volatile memory so need only be changed once not every time the sensor is powered These are stored in EEPROM using the P command The format of the commands required are P 0 highbyte r n P 1 lowbyte r n The full scale value is stored as a two byte number The target concentration must first be split into two bytes highbyte int concentration 256 low byte concentration 6256 concentration highbyte 256 For example to change a 5000ppm sensor FS to 2000 Highbyte int 2000 256 7 Low Byte 2000 256 208 and the relevant commands and responses are send P 0 7 r n response p 00007 00007 r n send P 1 208 r n response p 00001 00208 r n 46 f3Cco2Meter com CO2 Measurement Specialists Note that concentration MUST be expressed in the units used by the sensor For COZIR A mbient and MISIR the units are ppm For COZIR W ide Range the units are ppm 10 For 100 range sensors the units are ppm 100 Examples Target Full Scale Type High Byte Low Byte P
49. ure Temperature sensing is a measurement factory fit option U r n Zero point U r n U 33000 r n See Zero Point Calibration calibration using nitrogen u HHH r n Manual setting of u 32997 r n u 32997 r n See Zero Point Calibration the zero point X HHHH r n Zero point setting X 2000 r n X 32997 r n See Zero Point Calibration using a known gas calibration 11 f3CO2Meter com CO2 Measurement Specialists Command Use Example Response Comments Y r n Return firmware Y r n Returns two lines See Command Reference version and sensor for details serial number Z r n Return the most Z r n Z 01521 r n 1521ppm in the example recent CO2 measurement H H 4 r n Autocalibration 9 1 0 8 0 r n 1 0 8 0 r n See Autocalibration for configuration details Arm Return the A r n 00100 r n Multiply by 100 in the multiplier required example to convert the Z output to ppm r n Return r n See the Command configuration Reference for details information All communications are in ASCII and are terminated by carriage return line feed ASCII characters 13 and 10 This document uses the protocol r n to indicate the carriage return line feed All responses from the sensor including measurements have a leading space ASCII character 32 The character represents an ASCII representation of a numeric character 0 9 Note that there is a sp
50. ust be adjusted to take account of the decreased number of measurements For example if the sensor is used in command mode and powered up for only 10s every 5 minutes the autocalibration counter will run 30x slower than in streaming or polling mode so the autocalibration period should be adjusted to reflect that See COZIR Application Note Auto Calibration for details of the autocalibration set up The power level will depend on the duty cycle of the sensor It will typically be possible to achieve levels of less than 300uUW The digital filter will retain the last reading when switching into command mode and use this as its initial value when the sensor measurement is switched on again filtered output only If there is a very large step change between readings the filter may not reach a final stable value in one warm up cycle Users can avoid this potential issue by implementing their own signal conditioning using the unfiltered z output from the sensor The sensor will always power up in Streaming or Polling mode whichever was the last selected It will not power up in command mode this has to be selected by the user 39 11 11 Minimizing Power by Power Cycling f3CO2Meter com CO2 Measurement Specialists When there are very low levels of power available for example using a PV cell the best option is to power down the sensor between measurements Because of the short warm up times this approach can be used to run sensors ind
51. ways time an initial autocalibration interval first then settle into the regular autocalibration cycle The regular autocalibration timer is reset automatically if the user calibrates the sensor using the U G X F or u commands Before setting the auto calibration parameters please note the following e Before altering the auto calibration parameters switch the sensor into command mode send K 0 lt CR gt lt LF gt This stops the measurement process in the sensor e All commands must be terminated with Vn carriage return line feed NB HyperTerminal does not add the line feed character as standard The ASCII Setup must be configured to append line feeds 7 4 Autocalibration Intervals The autocalibration intervals are set using the command This command allows the autocalibration periods to be set interrogated or disabled To set the autocalibration intervals the command structure is initialinterval regularinterval r n Where both the initial interval and regular interval are given in days Both must be entered with a decimal point and one figure after the decimal point For example send 1 0 8 0 r n response 1 0 8 0 r n Will set the autocalibration interval to 8 days and the initial interval to 1 day Note that there is a space between the and the first number and a space between the two numbers In hex the example above reads 40 20 31 2E 30 20 38 2E 300D 0A 18 f3CO2Meter com CO2 Measurement Speci
52. y short initial inrush current at the start of each measurement cycle The peak is typically 33mA and is present for less than 1mS GSS recommends that the sensor supply circuit is capable of supplying a peak of 100mA Each measurement cycle lasts 30ms 40ms depending on the number of output fields being transmitted Between measurements cycles the power consumption reduces to 150 uW Current Profile K1 and K2 modes 30 500ms 25 20 15 Current mA 10 Time 34 f3CO2Meter com CO2 Measurement Specialists 11 6 Warm up Time When the sensor is powered up initially or when it is switched from command mode it must run through a short warm up period The COZIR warm up time comprises two parts start up cycle and signal processing delay The start up cycle takes 1 2s during which time the sensor will use approximately 6mJ of energy The first readings are transmitted by the sensor in streaming mode immediately following the start up cycle The signal processing delay depends on user settings The sensor has a low pass digital filter which smoothes the CO reading reported in the filtered CO output Z It takes some time for the digital filter to reach a final value This time depends on the digital filter setting which is user configurable To set the digital filter use the A command A r n where is the digital filter setting see COZIR Software Users Guide for more Information The warm up time must
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