manualshive.com logo in svg

TPS smartCHEM-D, Manual, Page: 34 / 60

Share
Download
TPS smartCHEM-D Manual Download Page 34

 

34

9.4 GLP Calibration Alarm 

A new feature of the 

smart

CHEM

-D

 is the GLP calibration alarm. The operator can select how 

often they wish to be reminded that the instrument requires calibration, and for which parameters 
they wish to be reminded.  

9.4.1 To set the GLP Calibration Alarm… 

1. Select the GLP Calibration Alarm menu (

 

→

→

 F5:GLP 

→

→

 F2:Alarm

). 

2. The calibration alarm period can now be selected… 

 GLP ALARM 
 F1:Daily   F2:1 Week 
 F3:2 Weeks F4:4 Weeks 
>F5:OFF 

The arrow indicates the current selection. 

Press 

 to be reminded that calibration is due every day. 

Press 

 to be reminded that calibration is due every week. 

Press 

 to be reminded that calibration is due every 2 weeks. 

Press 

 to be reminded that calibration is due every 4 weeks. 

Press 

 to switch the GLP Calibration Alarm system off. 

Press 

 to quit and retain the current setting. 

3. If 

, 

, 

 or 

 was pressed above, the 

smart

CHEM

-D

 will now allow the operator to select 

which parameters will be flagged with a calibration alarm… 

Select Channels 
 F1:Oxygen 
 F3:Conductivity/TDS 
 F5:Temperature 

Press the relevant 

 to 

 function key to select which parameter or parameters you would like 

to be flagged with a calibration alarm whenever calibration is due. Note the “ 

∗∗

 ” which appears 

next to the relevant parameter(s). 

Pressing the function key repeatedly adds and removes the “ 

∗∗

 

”. 

4. Press 

 to exit and save the selection. 

Summary of Contents for smartCHEM-D

Page 1: ...o enable you to find the information you need at a glance 2 Introduction The introduction has a diagram and explanation of the display and controls of the smartCHEM D It also contains a full listing of all of the items that you should have received with the unit Please take the time to read this section as it explains some of items that are mentioned in subsequent sections 3 Main Section The main ...

Page 2: ...Ltd ABN 30 009 773 371 4 Jamberoo Street Springwood Brisbane Australia 4127 Phone 07 32 900 400 International 61 7 32 900 400 Fax 07 3808 4871 International 61 7 3808 4871 Email tps tps com au Web www tps com au ...

Page 3: ...ctivity Calibration Messages 22 5 TDS Mode 23 5 1 Selecting TDS Mode 23 5 2 Setting the TDS calibration standard 23 5 3 TDS sensor k factor 23 5 4 TDS Calibration 24 5 5 TDS Calibration Notes 26 5 6 TDS Calibration Messages 26 6 Temperature Mode 27 6 1 Temperature Calibration 27 6 2 Temperature Calibration Notes 28 6 3 Calibration Messages 28 7 Auto Stability Function ASF 29 7 1 ASF During Normal ...

Page 4: ...atistical Software 42 12 5 Commands 43 12 6 Data Format 44 12 7 GLP Data Format 45 12 8 Importing Data into Microsoft Excel 46 13 Recorder Port 48 13 1 Recorder Port Configuration 48 13 2 Recorder Port Specifications 48 14 Setting the Clock 49 15 Initialising the smartCHEM D 50 16 Instrument firmware version number 50 17 Troubleshooting 51 17 1 General Errors 51 17 2 Dissolved Oxygen Troubleshooti...

Page 5: ...EM D Rear Panel Connectors Turn the retaining nut clockwise until it clicks into place when plugging in plastic connectors This is essential to produce a waterproof seal Always replace the waterproof cap when a connector is not in use to maintain waterproof integrity ...

Page 6: ...s to manually record readings into the Logger See section 11 1 Press to transmit current reading plus date and time to the RS232 port See section 12 2 Press to start and stop Automatic Datalogging See section 11 2 Press to accept default values or those entered on the Numeric Keypad 1 5 Numeric Keypad Used to enter values during set up and calibration A decimal point is provided 1 6 Delete Key Pre...

Page 7: ...nsor 123400 2 1m Cable for ED1 DO2 sensor 123228 3 YSI Non stirring DO2 sensor for BOD bottles 123214 4 YSI Self stirring DO2 sensor for BOD bottles 123213 5 YSI Field type DO2 sensor 123204 6 1m Cable for YSI Field DO2 sensor 123212 7 k 0 1 ATC Temp Conductivity TDS Sensor 122232 8 k 10 ATC Temp Conductivity TDS Sensor 122234 Instrument Options 1 Flexible arm type electrode holder 130088 2 RS232 ...

Page 8: ...ected range 0 to 300 0 Saturation 300 to 450 Saturation 0 1 Saturation 1 Saturation 0 3 Saturation 0 to 60 0 Gaseous 60 to 100 Gaseous 0 1 Gaseous 1 Gaseous 0 1 Gaseous Note Ranges are automatically selected Exact auto ranging points and full scales are subject to sensor performance Sensor Type Clark type polarographic sensor with in built ATC Salinity Correction 0 to 50 0 ppK automatic using cond...

Page 9: ...selected range at 25 O C k 10 Sensor 0 to 200 0 µS cm 0 to 2000 µS cm 0 to 20 00 mS cm 0 to 200 0 mS cm 0 1 µS cm 1 µS cm 0 01 mS cm 0 1 mS cm 0 5 of full scale of selected range at 25 O C Note Ranges are automatically selected Exact auto ranging points and full scales are subject to sensor performance Sensor Type Glass body with two platinised platinum plates In built ATC Temperature Compensation...

Page 10: ...ge at 25 O C k 10 Sensor 0 to 100 0 ppM 0 to 1000 ppM 0 to 10 00 ppK 0 to 100 0 ppK 0 1 ppM 1 ppM 0 01 ppK 0 1 ppK 0 5 of full scale of selected range at 25 O C Note Ranges are automatically selected Exact auto ranging points and full scales are subject to sensor performance Sensor Type Glass body with two platinised platinum plates In built ATC Temperature Compensation Automatic 0 to 100 O C Cali...

Page 11: ...9200 38400 baud 8 bits no parity 1 stop bit XON XOFF Protocol Clock Calendar clock displays date month year hours minutes seconds Good Laboratory Practices Date time and results of last calibration for all parameters are stored This information can be recalled or sent to the RS232 port at any time Power 12V DC 90 mA backlight off 130 mA backlight on AC DC adaptor to suit country of destination is ...

Page 12: ...t F3 Print F4 Program F1 Secs F2 Mins F3 Hours F3 Mode F1 ppM F2 ppM Sal F3 Sat F4 Gas F5 Cond F6 TDS F4 Setup F1 Standards F1 Cond F3 TDS F2 Clock F3 Backlight F1 On F2 Off F3 Energy Saver F4 Ports F1 Baud Rate F3 Enable Stirrer or F3 Disable Stirrer F5 Recorder F5 Initialise F1 All F5 GLP F1 Recall F2 Alarm F1 Daily F2 1 Week F3 2 Weeks F4 4 Weeks F5 OFF F3 Print F6 Access F1 Change code F3 Enab...

Page 13: ...s available at the Accessories connector on the rear of the smartCHEM D When using the YSI self stirring BOD sensor part number 123213 please use the optional adaptor cable part number 123311 The Control output is capable of supplying 150 mA which is ample for the two stirrers detailed above 3 2 1 Enabling and Disabling the Dissolved Oxygen Stirrer Output 1 Select the Ports menu F4 Setup F4 Ports ...

Page 14: ...his solution may be prepared by dissolving 2g of Sodium Sulphite in 100mL of distilled water A 50g bottle of Sodium Sulphite powder part number 123302 is supplied with a new Dissolved Oxygen sensor for this purpose 2 Allow the reading to stabilise at or near zero This may take 2 3 minutes 3 Select Oxygen Calibration F1 Calibrate F1 Oxygen When the reading is below approximately 25 Saturation 2 ppM...

Page 15: ...O C Oxygen AIR Cal Press Enter 3 Press to calibrate The Automatic Stability Function will now show a and highlight any unstable readings 101 0 S 25 0 O C Oxygen AIR Cal Waiting to Stabilise When the Dissolved Oxygen and Temperature readings have both stabilised the unit will calibrate itself To calibrate immediately without waiting for complete stability press to disable the Automatic Stability Fu...

Page 16: ...ke up to 5 minutes 3 Select Oxygen Calibration F1 Calibrate F1 Oxygen When the reading is above approximately 2 ppM the smartCHEM D will display the AIR SPAN calibration screen Note the cursor underlining the A in AIR 9 00ppMs 25 0 O C Oxygen AIR SPAN Cal Press Enter Use the numeric keypad to enter the Dissolved Oxygen value of the solution The words AIR SPAN are deleted and the value being entere...

Page 17: ...ormed at least weekly Of course more frequent calibration will result in greater confidence in results 5 All calibration information is retained in memory when the smartCHEM D is switched off This information can be recalled or printed later using the GLP function see section 9 3 5 Dissolved Oxygen Calibration Messages 1 If a Zero calibration has been successfully performed the smartCHEM D will di...

Page 18: ...5 0 5 The smartCHEM D will display the following message if the calibration point is too high The unit must be calibrated in the lower of the two ranges that are provided for each Oxygen mode Oxygen OvrRange Not Calibrated 6 The allowable Span range for a Dissolved Oxygen sensor is 65 0 to 200 0 If calibration fails due to the Span value being outside these limits then please consult the Troublesh...

Page 19: ...e standard solution Alternatively press to quit without changing the current setting 4 The smartCHEM D will now ask you to enter the units for the Conductivity standard Conductivity Standard 2760 Select Units F1 uS cm F2 mS cm Press to set the Conductivity Standard as µS cm Press to set the Conductivity Standard as mS cm 5 The Conductivity standard is now programmed for use at calibration 4 3 Cond...

Page 20: ... the outside of the sensor dry DO NOT BLOT THE ELECTRODE PLATES Zero Calibration 3 Let the sensor dry in air 4 Select Conductivity Calibration F1 Calibrate F3 Cond 5 The smartCHEM D will recognise the low conductivity signal and attempt a Zero calibration For example Cond 0 01uS ZERO Calibration Press Enter 6 Press to calibrate The Automatic Stability Function will now show a and highlight the rea...

Page 21: ...onductivity standard to be used For example Cond 2 86mS 2760 uS Calibration Press Enter 8 Press to calibrate The Automatic Stability Function will now show a and highlight the reading while it is unstable Cond 2 86mS 2760 uS Calibration Waiting to Stabilise When the Conductivity reading has stabilised the unit will calibrate itself To calibrate immediately without waiting for complete stability pr...

Page 22: ...it will attempt to calibrate Ensure that the standard value displayed corresponds to the standard that you are using Alter the Standards set up if necessary see section 4 2 6 Calibration settings for k 0 1 k 1 0 and k 10 sensors are NOT stored separately The smartCHEM D requires re calibration when a new k factor sensor is connected 4 6 Conductivity Calibration Messages 1 If a Zero Calibration has...

Page 23: ...he standard solution Alternatively press to quit without changing the current setting 4 The smartCHEM D will now ask you to enter the units for the TDS standard TDS Standard 2000 Select Units F1 ppM F2 ppK Press to set the TDS Standard as ppM Press to set the TDS Standard as ppK 5 The TDS standard is now programmed for use at calibration 5 3 TDS sensor k factor The smartCHEM D automatically recogn...

Page 24: ...of the sensor dry DO NOT BLOT THE ELECTRODE PLATES Zero Calibration 3 Let the sensor dry in air 4 Select TDS Calibration F1 Calibrate F3 TDS 5 The smartCHEM D will recognise the low TDS signal and attempt a Zero calibration For example TDS 0 01ppM ZERO Calibration Press Enter 6 Press to calibrate The Automatic Stability Function will now show a and highlight the reading while it is unstable TDS 0 ...

Page 25: ... standard to be used For example TDS 2 10ppK 2000 ppM Calibration Press Enter 8 Press to calibrate The Automatic Stability Function will now show a and highlight the reading while it is unstable TDS 2 10ppK 2000 ppM Calibration Waiting to Stabilise When the TDS reading has stabilised the unit will calibrate itself To calibrate immediately without waiting for complete stability press to disable the...

Page 26: ...ich it will attempt to calibrate Ensure that the standard value displayed corresponds to the standard that you are using Alter the Standards set up if necessary see section 5 2 6 Calibration settings for k 0 1 k 1 0 and k 10 sensors are NOT stored separately The smartCHEM D requires re calibration when a new k factor sensor is connected 5 6 TDS Calibration Messages 1 If a Zero Calibration has been...

Page 27: ...olved Oxygen sensor plug the Dissolved Oxygen sensor into the Oxygen socket and ensure that the separate Temperature is not connected 2 Switch the meter on 3 Place the Temperature or Dissolved Oxygen sensor into a beaker of room temperature water alongside a good quality mercury thermometer Stir the probe and the thermometer gently to ensure an even temperature throughout the beaker 4 Select Tempe...

Page 28: ... 1 If a temperature calibration has been successfully performed the smartCHEM D will display the following message and the offset of the sensor Calibration OK Offset 0 1 O C 2 If a temperature calibration has failed the smartCHEM D will display the following message and the failed offset value of the sensor Calibration Failed Offset 11 0 O C 3 The smartCHEM D has an allowable Offset range of 10 0 ...

Page 29: ...d in case user intervention is required 2 When ALL parameters have stabilised all highlighting will be removed and the will change to a All readings are now frozen For example 99 8 S 25 0O C 2760 uS 31 12 01 12 00 00 3 The operator can now make a note of the reading as required 4 Press again to re start the ASF sampling process 5 Press a second time while the symbol is being displayed to turn ASF ...

Page 30: ...omes unstable the highlighting is applied again The highlighting is provided to give the operator a visual indication of exactly which parameters have not stabilised in case user intervention is required 2 When ALL parameters have stabilised all highlighting will be removed and the will change to a All readings are now frozen and will be recorded into memory For example 99 8 S 25 0O C 2760 uS 31 1...

Page 31: ...required 2 When ALL parameters have become stable all highlighting will be removed and the will change to a All readings are now frozen and automatic datalogging has stopped For example 99 8 S 25 0O C 2760 uS 31 12 01 12 00 00 3 To unfreeze the display in order to take the next reading press and again to re start the ASF automatic datalogging process 4 Press a second time while the symbol is being...

Page 32: ... 12 01 12 00 Oxygen Span 100 0 31 12 01 12 10 Oxygen Calibrated F4 Next 5 Press to sequentially scroll through the GLP information for all parameters Press to scroll back to previous data The sequence of information displayed is shown below Press to abort at any time GLP Display sequence smartCHEM D V1 0 S1234 31 12 01 15 00 Oxygen Zero 0 1 31 12 01 12 00 Oxygen Span 100 0 31 12 01 12 10 Oxygen Ca...

Page 33: ...r or PC via the RS232 port 1 Switch the meter on 2 Connect one end of the RS232 cable to the Power RS232 socket of the smartCHEM D 3 Connect the other end of the RS232 cable to an RS232 Printer or to a Serial port on a PC 4 Send the GLP information to the RS232 port F5 GLP F3 Print The message Printing GLP Data is displayed while sending the data to the RS232 port 5 The GLP information is sent to ...

Page 34: ...ed that calibration is due every week Press to be reminded that calibration is due every 2 weeks Press to be reminded that calibration is due every 4 weeks Press to switch the GLP Calibration Alarm system off Press to quit and retain the current setting 3 If or was pressed above the smartCHEM D will now allow the operator to select which parameters will be flagged with a calibration alarm Select C...

Page 35: ...en if the unit is not calibrated on that day For example if the GLP Calibration Alarm is triggered weekly on a Monday and the meter is finally calibrated the following Wednesday the next GLP Calibration Alarm will still be on the following Monday 9 5 Instrument Serial Number In case the serial number that is fitted to the rear of the smartCHEM D is removed or becomes illegible it is also available...

Page 36: ...r verification New Access code _ Re Enter to Verify Re enter the access code as per the previous step Press to quit without enabling the Access Code system 5 The smartCHEM D now confirms that the Access Code system is enabled before returning to the Access Code menu 10 2 Using the Access Code System When the Access Code system is enabled as per section 10 1 the smartCHEM D prompts the operator to ...

Page 37: ...t changing the Access Code 4 The smartCHEM D now prompts you to re enter the access code for verification New Access code _ Re Enter to Verify Re enter the access code as per the previous step Press to quit without changing the Access Code 5 The smartCHEM D now confirms that the Access Code system is enabled before returning to the Access Code menu 10 4 Disabling the Access Code System 1 Select th...

Page 38: ... must be programmed then automatic logging can be started and stopped as required 1 Select the Logger menu F2 Logger 2 Select F4 Program from the menu The display should now look similar to that shown below The current Logging Printing Period is displayed Enter Logging Print Period 0 secs 3 Use the Numeric Keypad to set the period at which the smartCHEM D will automatically log records into memory...

Page 39: ...g automatic datalogging The stirrer output can still be activated manually during automatic datalogging 7 The automatic logging function is now programmed and can be started and stopped as required 8 To start automatic logging press in normal display mode When the smartCHEM D is logging into its own memory the display will look like this 10 0 S 25 0O C 2760uS 31 12 01 Log 1 12 00 00 The log number...

Page 40: ...ress and to move forwards and backwards through the records Press and hold or to scroll continuously through the readings The rate is slow enough to allow the operator to see trends in the data as it is scrolling To display a specific record type in the desired record number using the Numeric Keypad and press Press to send the displayed record to the RS232 port 11 4 Erasing Records from the Logger...

Page 41: ...l port of a PC 3 Ensure that the baud rate for the printer or PC and the smartCHEM D are the same If necessary alter the baud rate of the smartCHEM D see section 12 1 The smartCHEM D uses XON XOFF protocol Ensure that the printer is set accordingly 4 Select the Logger menu F2 Logger 5 Select F3 Print from the menu 6 Printing starts as soon as is pressed The display shows the word Printing until pr...

Page 42: ...c datalogging See section 11 2 for details Press while recalling data on the display see section 11 3 to send that record to the RS232 port 12 3 RS232 Configuration The smartCHEM D RS232 configuration is 8 Bits No Parity 1 Stop Bit XON XOFF Protocol This information is displayed when setting the baud rate see section 12 1 12 4 Communication and Statistical Software Communication between the smartC...

Page 43: ...ngs in memory for example smartCHEM D V1 0 S1234 1489 m cr where are spaces Note that the number of logged readings is right justified The m is present when the Dissolved Oxygen stirrer is enabled section 3 2 1 and the is used internally by the WinTPS software Request GLP information G cr Returns all calibration GLP information plus the instrument model serial number and current date see section 1...

Page 44: ...se m ppM for parts per Million readout with Salinity correction applied Note the upper case M S for Saturation readout G for Gaseous readout CCCCCCC is the Conductivity or TDS data 7 characters right justified uuu is the Conductivity TDS units description which can be any of the following uS for µS cm Conductivity readout mS for mS cm Conductivity readout ppM for parts per Million TDS readout ppK ...

Page 45: ...ter after receiving each line For example smartCHEM D V1 0 S1234 31 12 2001 15 00 Oxygen Zero 0 1 31 12 2001 12 00 Oxygen Span 100 0 31 12 2001 12 10 Conductivity Zero 0 01uS 31 12 2001 12 20 Conductivity k 1 01 31 12 2001 12 30 TDS Zero 0 01ppM 31 12 2001 12 40 TDS k 1 01 31 12 2001 12 50 Temp Probe Offset 1 0oC 31 12 2001 14 40 Temp ED1 Offset 1 0oC 31 12 2001 14 50 Ends ...

Page 46: ...xt Files prn txt csv 3 Navigate to the folder where your data file is stored and double click it to start the Text Import Wizard Note The default data folder for the WinTPS software is C My Documents WinTPS 4 In step 1 of the Text Import Wizard select Fixed width as per the sample screen below then press Next Note that the data column headers in row 1 appear only when the data is downloaded using ...

Page 47: ...X axis is correctly formatted if the data is to be charted later Press Next after all the column breaks have been inserted 6 Simply press Finish at step 3 of the Text Import Wizard TPS recommends that the data format for each column be set once the data is in spreadsheet format For help on formatting the data columns charting graphing or other operations please consult the Microsoft Excel help fil...

Page 48: ...mperature data Press to quit and retain the current setting 13 2 Recorder Port Specifications Mode Range Output Range Examples Reading mV Out Dissolved Oxygen 0 00 to 40 0 ppM 0 0 to 500 Sat n 0 0 to 100 Gas 0 to 2000 mV 0 00 ppM 0 mV 100 0 Sat n 400 mV Conductivity 0 to 3 000 µS cm 0 to 30 00 µS cm 0 to 300 0 µS cm 0 to 3000 µS cm 0 to 30 00 mS cm 0 to 300 0 mS cm 0 to 2000 mV for full scale of s...

Page 49: ...ll now show the current date for example Date is now 04 09 01 Enter Date 04 09 01 dd mm yy 5 Use the Numeric Keypad to enter the current date then press Alternatively press menu to quit and retain the current setting Notes 1 The smartCHEM D tests that a valid day of the month is entered If an invalid date is entered eg 31 02 2001 the smartCHEM D beeps and displays the message Invalid Date The mete...

Page 50: ...HEM D 1 Select Initialise from the Setup menu F4 Setup F5 Initialise 2 The smartCHEM D now asks if you are sure that you wish to initialise ALL parameters Initialise F1 All Press to initialise ALL parameters reset all factory default settings and clear the memory 3 When returning the meter to normal display mode note that the decimal points have been replaced with a to indicate that each parameter...

Page 51: ...tly pump the pressure compensation diaphragm several times Membrane should be smooth and convex with no wrinkles Re fit membrane if necessary Replace membrane and re fill electrode Return electrode to factory for repair or replacement Blackened Silver anode Electrode has been exposed to sulphides or other chemical poisoning ED1 Remove barrel and soak in 5 Ammonia solution for 10 minutes If anode i...

Page 52: ... is greater than 25 below the nominal value 1 Standard solution is inaccurate 2 Sensor may have a build up of conductive material such as salt 3 Sensor is faulty 4 Faulty instrument Replace standard solution Clean sensor as per the instructions detailed in section 18 2 1 Return sensor to factory for repair or replacement Return to factory for repair Inaccurate readings even when calibration is suc...

Page 53: ...r is connected or vice versa Re calibrate the Temperature reading on the new sensor Meter only keeps Temperature calibration data for one Dissolved Oxygen sensor Displays flashing M when Temperature and or Dissolved Oxygen sensor plugged in 1 Faulty instrument socket 2 Faulty Dissolved Oxygen or Temperature sensor whichever is being calibrated 3 Faulty Dissolved Oxygen cable if Dissolved Oxygen se...

Page 54: ...rane permeability This coefficient is 4 2 o C at 25o C for this thickness membrane A polarising voltage of about 800 millivolts is applied between the two electrodes The gold electrode is placed close to the membrane and because of the polarising voltage oxygen diffusing through the membrane will be reduced at the gold electrode Equation O2 2H 2 electrons H2O2 This reduction process will produce a...

Page 55: ... exerts about 15 5 cm of Mercury pressure Water in equilibrium with air and with no oxygen demand C O D B O D etc is saturated and has this dissolved oxygen partial pressure If we define 100 Saturation in Partial Pressure terms then 15 5 cm Hg 100 Saturation This is a practical unit to use The probe linear readout is then a linear function of Saturation Organic cell walls behave like the probe and...

Page 56: ...Membrane Workers have shown that the relationship between the diffusion current oxygen current and the external velocity of the liquid is expotential Some workers using thicker membranes have shown even less dependence of the diffusion current on liquid velocity Because of the expotential nature of the relationship considerable changes in velocity have to be made before noticing any change in the ...

Page 57: ...rinse well with distilled water Conductivity sensors can be stored dry Ensure that the sensor is stored in a covered container to avoid dust and dirt build up Cleaning Conductivity of Sensors Platinised platinum Conductivity sensors can only be cleaned by rinsing in a suitable solvent DO NOT wipe the electrode plates as this will remove the platinum black layer 1 Rinsing in distilled water will re...

Page 58: ...e the electrode in platinising solution at least to the vent hole in the glass body Platinising solution is available from TPS part no 122300 Alternatively platinising solution can be prepared by dissolving 1g of Hydrogen Chloroplatinate H2PtCl16 in 30mL of distilled water and including about 0 01g of Lead Acetate CH3COO 2Pb and a drop or two of concentrated HCl Caution This is a dangerous solutio...

Page 59: ...hat this equipment is in need of repair please re read the manual Sometimes instruments are received for repair in perfect working order This can occur where batteries simply require replacement or re charging or where the electrode simply requires cleaning or replacement TPS Pty Ltd has a fine reputation for prompt and efficient service In just a few days our factory service engineers and technic...

Page 60: ...60 ...

Reviews:

No comments