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The barometer measures pressure in a very small range around sea level atmospheric pressure (0.8 to 1.05 atm, 81 to 106 kPa, or 608 to 798 mm Hg). Make sure that the barometer is not being used to measure pressures that lower or higher than the range of the device.

If the barometer readings do not agree well with the barometric pressure reported by a local airport or television station, it is likely because the reported pressure is a corrected value. If you want your barometer to read sea-level pressure (to compare with a television station), adjust the barometer's readings with the offset potentiometer. Use a small jeweler's screwdriver to tune the potentiometer which is positioned in a hole on one end of the barometer. It is a 15-turn potentiometer, allowing for gradual adjustment.

SPECIFICATIONS

Sensing Element: SenSym SDX15A4
Pressure Range: 0.8 to 1.05 atm (25 to 31.5 in Hg)
Maximum Pressure that the sensor can tolerate without permanent damage: 30 psi or 61 in Hg or 207 kPa
Sensitivity: 436 mV/in Hg or 13.06 V/atm
Resolution: 0.003 inHG
Combined linearity and hysteresis: typical +/-0.1% full scale, maximum +/-0.5% full scale
Response time: 100 microseconds

CALIBRATION

TN B02 [Why doesn’t my barometer read the same as the weather forecast?]

Each barometer is calibrated before shipping. If your barometer readings do not agree with the local airport or television station, it is because you are looking at two different kinds of readings. Station pressure is the true pressure at your site, or station. This is the pressure a mercury barometer would read at your location. This is also the pressure that your Forston Labs barometer is calibrated to read. [Sea-level pressure] is the pressure after the station pressure has been adjusted to its equivalent at sea level. Airports and television stations usually report the sea-level pressure rather than the station pressure. This is commonly done to take the eddect of altitude on atmospheric pressure out of the equation for weather forecasters. The barometric formula is explained along with boxes to input the information from your local television station or airport. Your true station pressure is reported in mm Hg, in Hg, and kPa. You can use the barometer as a weather station If you want your Forston Labs barometer to read sea-level pressure instead of station pressure: There is an offset potentiometer that you can use to adjust the pressure reading up and down. There is a small hole on one end of the Barometer with a small slotted screw inside. A small jeweler's screwdriver can be used to turn this screw. This is a 15-turn potentiometer, so the adjustment can be made very gradually. Simply monitor the readings from the barometer and adjust the screw until the readings match the airport or television station readings.

TN CA01 [Calcium Ion-Selective Electrode Troubleshooting and FAQs]

TROUBLESHOOTING

Primary Test: Check the raw voltages while measuring the standard solutions. The high concentration standard (1000 mg/L) should give a reading of around 1.9 volts. The low concentration standard (10 mg/L) should give a reading of around 1.5 volts.

Secondary Test: Refer to TN I01: General tips for using Ion Selective Electrodes (ISE).

SPECIFICATIONS

Range: 0.20 to 40,000 mg/L or ppm (5 X 10-6 M to 1.0 M)
Resolution: (% of reading, low scale reading, high scale reading): 1.4% of reading (0.20 ±0.0028 or 40,000 ±560 mg/L)
pH Range: 3 to 10
Interfering Ions: Pb2+, Hg2+, Sr2+, Cu2+, Ni2+
Electrode Slope: +28 mV/decade
Approximate Calibration Voltages:
- High (1000 mg/L) 1.9 V
- Low (10 mg/L) 1.5 V
Electrode Resistance: 1 to 4 MΩ
Reproducibility: ± 5% of reading
Temperature range: 0 to 50ºC (no temperature compensation)
Minimum immersion: 1 inch
Electrode length: 155 mm
Body diameter: 12 mm
Cap diameter: 16 mm
Cable length: 100 cm

CALIBRATION

Do I need to calibrate the calcium ion-selective electrode? Yes. Conduct a two-point calibration using the standard solutions that are shipped with the sensor. The ISE should be soaked in the high concentration (1000 mg/L) standard. Enter the concentration value of the high concentration standard. Remove the ISE from the high standard, rinse well with distilled water from a wash bottle, and gently blot dry with a paper towel or lab wipe. Place the electrode into the low (10 mg/L) concentration standard. Enter the concentration value of the low concentration standard.

IMPORTANT: Make sure the ISE is not resting on the bottom of the container, and that the small white reference contacts are immersed. Make sure no air bubbles are trapped below the ISE.

Hold the ISE still and wait for the voltage reading to stabilize. Enter the concentration value of the low concentration standard. The calibration should now be complete and you can measure values for samples.

TN CL01 [Chloride Ion-Selective Electrode Troubleshooting and FAQs]

TROUBLESHOOTING

Primary Test: Check the raw voltages while measuring the standard solutionss. The high concentration standard (1000 mg/L) should give a reading of around 2.0 volts. The low concentration standard (10 mg/L) should give a reading of around 2.7 volts.

Secondary Test: Refer to TN I01: General tips for using Ion Selective Electrodes (ISE).

SPECIFICATIONS

Range: 1.8 to 35,500 mg/L or ppm (5 X 10-5 M to 1.0 M)
Resolution: (% of reading, low scale reading, high scale reading): 0.7% of reading (1.8 ±0.013 or 35,500 ±250 mg/L)
pH Range: 2 to 12
Interfering Ions: CN-, Br-, I-, S2-
Electrode Slope: ≃56 mV/decade
Approximate Calibration Voltages:
- High (1000 mg/L) 2.0V
- Low (10 mg/L) 2.8 V
Electrode Resistance: 1 to 4 MΩ
Reproducibility: ± 5% of reading
Temperature range: 0 to 50ºC (no temperature compensation)
Minimum immersion: 1 inch
Electrode length: 155 mm
Body diameter: 12 mm
Cap diameter: 16 mm
Cable length: 100 cm

CALIBRATION

Conduct a two-point calibration using the standard solutions that are shipped with the sensor. The ISE should be soaked in the high concentration standard. Enter the concentration value of the high concentration standard. Remove the ISE from the high concentration standard, rinse well with distilled water from a wash bottle, and gently blot dry with a paper towel or lab wipe. Place the electrode in the low concentration standard. Enter the concentration value of the low concentration standard.

IMPORTANT: Make sure the ISE is not resting on the bottom of the container, and that the small white reference contacts are immersed. Make sure no air bubbles are trapped below the ISE.

Hold the ISE still and wait for the voltage reading to stabilize. The calibration should now be complete and you can measure values for samples.

TN CO01 [CO2 Gas Sensor Troubleshooting and FAQs]

TROUBLESHOOTING

Primary Test: Plug in the sensor, start up the data-collection program and allow the sensor to warm up for at least 90 seconds. Exhale your breath directly on the shaft of the sensor. You should see an increase in CO2 levels.

SPECIFICATIONS

Measurement range: 0 - 5000 ppm CO2 (old model); 1-10,000 ppm and 0-100,000 ppm (new model)
Accuracy
- +/- 100 ppm or +/- 10% of reading (low range)
- +/- 100 ppm or +/- 20% of reading (high range)
Typical Resolution: 3 ppm (low range); 30 ppm (high range)
Response Time: 95% of full scale reading in 120 seconds
Warm up time: 90 seconds
Pressure effect: 0.19% of reading/mm Hg from standard pressure
Output signal range: 0 - 4.0 V
Input potential: 5V (+/- 0.25 V)
Gas sampling mode: diffusion
Normal operating temperature range: 25 deg C (+/- 5 deg C)
Operating humidity range: 5 - 95% (non-condensing)
Storage temperature: -40 to 65 deg C

CALIBRATION

Does the CO2 gas sensor need to be calibrated? Usually not. If you find that you need to calibrate your CO2 gas sensor, it can be calibrated using a single CO2 level based upon a sample of outside air which has a uniform CO2 concentration of 380 ppm. Note: This calibration method is different from the usual two-point calibration performed using other Forston Labs sensors. See the product manual for detailed instructions on how to calibrate the CO2 has sensor.

If you wish to reset the CO2 Gas Sensor to its factory default calibration values, press and hold the calibration button for approximately 5 seconds. The red light will change from flashing to steady. When the light turns off, the sensor will be back to its factory settings.

TN CO02 [Tips for using the CO2-O2 Tee]

The CO2-O2 Tee is designed to be used with a CO2 gas sensor, an O2 gas sensor and a 250 mL Nalgene bottle. The tapered end of the Tee fits into the neck of the Nalgene bottle. The CO2 gas sensor should be put in the Tee directly across from the bottle. The O2 gas sensor fits snugly in the top of the Tee. The entire assembly should be positioned so that the bottle and CO2 gas sensor are horizontal and the O2 gas sensor is vertical.

You may need to put a layer of tape around the tapered end of the Tee to produce a tight fit. Tolerances for the dimensions of Nalgene bottles are set to the outer diameter of the opening so inside diameters may vary.

TN CO03 [What are the CO2 gas sensor power requirements? Can I use two CO2 gas sensors at the same time?]

When two CO2 gas sensors are connected at the same time, the amount of current drawn exceeds the maximum current output of the interface. Due to this limitation, only one CO2 gas sensor can be used at a time.

The CO2 gas sensor draws about 160 mA each time it flashes. This is a substantial current that can cause problems when it is powered by batteries or used in conjunction with some other sensors.

Note: the CO2 gas sensor does not need to be calibrated. You can check it by reading its signal in fresh air. It should read about 0.2 V. If you exhale your breath on it, the reading should go to the maximum value of 2.5 V. The procedure for recalibration is in the manual.

TN COL01 [Colorimeter Troubleshooting and FAQs]

TROUBLESHOOTING

Primary Test: Connect the colorimeter to a LabNavigator. Allow the colorimeter to warm up for 5 minutes. Place a cuvette, about 3/4 full of distilled water, in the colorimeter and close the lid. Select a wavelength. Press and hold the CAL button on the colorimeter. When the red LED begins to flash, release the CAL button. When the red LED stops flashing, the colorimeter is calibrated. Check the absorbance readings, which should be very nearly zero.

Secondary test: Prepare a solution with a color (a simple test solution for the 635 nm wavelength setting can be made by adding 2 drops of green food coloring to 100 mL of tap water). After calibrating the Colorimeter, fill a cuvette about 3/4 full with the test solution. Place the cuvette in the Colorimeter and close the lid. The absorbance readings should change. You may dilute the test solution and place a cuvette of the dilute solution in the Colorimeter to check the change in absorbance.

The normal, most useful absorbance range is 0.05 - 1.0, or 10% - 90% transmittance.

SPECIFICATIONS

Range: 0 to 3 (absorbance)
Useful Range 0.05 to 1.0 (absorbance) and 90% to 10% transmittance (%T)
Wavelengths: 430 nm, 470 nm, 565 nm, 635 nm
Resolution: 0.035 %T
Supply voltage: 5VDC +/- 25 mV
Supply current (typical): 40 mA
Power up time: 700 ms (maximum)
Output voltage range: 0 - 4 V
Transfer function: Vout = 0.035 x (%T) + 0
Stored calibration values: Slope = 28.571; Intercept = 0

CALIBRATION

Calibration? Yes, each time before use. After powering up the Colorimeter and waiting for a 5 minute warm up, press the < or > button on the Colorimeter to select a wavelength. Open the lid, insert a cuvette filled about 3/4 full of distilled water, and close the lid. Make sure that one clear side of the cuvette is lined up with the arrow at the top of the cuvette slot. Press the CAL button and hold it unTN the red LED begins to flash and then release the CAL button. When the LED stops flashing, the calibration is complete.

TN COL02 [Where can I get glass or quartz cuvettes for your Colorimeter or spectrophotometers?]

Glass and quartz cuvettes are available from Starna Cells, Inc., www.starnacells.com, 805-466-8855. Models that work with our Colorimeter and spectrophotometers include:

Optical Glass (334-2500 nm), 10 mm path length, two polished sides, Starna order code 1/G/10.

Spectrosil Quartz (170-2700 nm), 10 mm path length, two polished sides, Starna order code 1/Q/10.

TN COL03 [My Colorimeter is not working properly. What should I do?]

If you have followed the instructions carefully and the Colorimeter does not seem to be working properly, call Forston Labs Technical Support. If the problem cannot be solved over the phone, we will issue you a Return Authorization number to send it in for a free inspection. If there is a manufacturing defect in the Colorimeter, we will repair or replace it at no charge. Often, however, Colorimeters malfunction because they have had liquid spilled inside causing corrosion. If this is the case, we will let you know if it can be repaired or if it is beyond repair.

TN CT01 [Conductivity Probe Troubleshooting and FAQs]

TROUBLESHOOTING

Primary Test: Place the toggle switch at the desired setting, run the data-collection program, and take a reading in a solution of known TDS. Suggest using the calibration solution that comes with the probe. It is 500 mg/L TDS or 1000 microsiemens/cm.

Secondary Test: If you change the setting of the toggle switch while LabNavigator is running, reset the program so that the calibration equation for the new setting is selected.

SPECIFICATIONS

Range of Conductivity Probe:
- Low Range: 0 to 200 microsiemens/cm (0 to 100 mg/L TDS)
- Mid Range: 0 to 2000 microsiemens/cm (0 to 1000 mg/L TDS)
- High Range: 0 to 20,000 microsiemens/cm (0 to 10,000 mg/L TDS)
Resolution:
- Low Range: 0.1 microsiemen/cm (0.05 mg/L TDS)
- Mid Range: 1 microsiemen/cm (0.5 mg/L TDS)
- High Range 10 microsiemen/cm (5 mg/L TDS)
Accuracy: +/-1% of full-scale reading for each range
Response Time: 98% of full-scale reading in 5 seconds, 100% of full-scale in 15 seconds
Temperature Compensation: automatic from 5 to 35 deg C
Temperature Range(can be placed in): 0 to 80 deg C
Cell Constant: 1.0 1/cm
Description: ABS body, parallel carbon (graphite) electrodes
Dimensions: 12 mm OD amd 150 mm length

CALIBRATION

You may calibrate the probe using LabNavigator. The calibration units can be microsiemens/cm, mg/L, mg/L as NaCl, or salinity in ppt.

Select the conductivity range setting on the probe box. Perform the zero calibration point with the probe in the air. A very small voltage reading will be displayed; call this value 0. Place the probe in a standard solution (a solution of known concentration), such as the NaCl standard solution that is packaged with the probe. Be sure that the entire elongated hole in the tip of the probe is immersed. When the voltage readings settle, enter the value for the standard solution in the desired units. For better results, you can calibrate the probe with two standard solutions. It is wise to select standards with concentrations above and below the readings that you anticipate taking with the probe during the procedure.

TN CT02 [Do you sell Conductivity Standards?]

Yes, we sell one Conductivity Standard for each of the Conductivity Sensor's three ranges. Each standard contains 500 mL.

TN DO01 [Dissolved Oxygen Probe Troubleshooting and FAQs]

TROUBLESHOOTING

Primary Test: Is the D.O. Probe connected to an interface with a pH, Conductivity, ISE, or Direct-Connect Temperature Probe? If so, remove the other sensors while using the D.O. Probe.

Primary Test: Make sure that the probe is placed in a large container or water and that the sensor is gently swirled during data collection.

Secondary Test: If calibration is unsatisfactory, remove and refill the membrane cap with electrode solution and calibrate the probe again.

Secondary Test: Check for an air bubble inside the membrane cap.

SPECIFICATIONS

Range: 0 to 15 mg/L (or ppm)
Accuracy: +/-0.2 mg/L
Resolution: 0.007 mg/L
Response Time: 95% of final reading in 30 seconds, 98% in 45 seconds
Temperature Compensation: automatic from 5 to 35 deg C
Pressure Compensation: manual, accounted for during calibration
Salinity Compensation: manual, accounted for during calibration
Minimum Sample Flow: 20 cm/s

CALIBRATION

Calibrate? Not always. If your process seeks to measure only a change in dissolved oxygen then the stored calibration is suitable. If you plan to make discrete measurements of dissolved oxygen in a natural body of water, then calibration is recommended.

The calibration process for this sensor is lengthy. Refer to the product manual for detailed instructions.

TN DO02 [Suggestions for using the Dissolved Oxygen Probe.]

We receive very few Dissolved Oxygen Probes back for repair. The probes are rather robust, and if used properly very accurate.

Most people who experience difficulty with DO Probes do so because they do not have the proper calibration procedures to follow. The procedure for calibration can be found in the DO Probe product manual.

If the calibration procedure is followed carefully, the readings from the Dissolved Oxygen Probe are as accurate, and more precise, than a DO titration test.

Below are some general tips to follow when working with the Dissolved Oxygen Probe:

A) Do you really need to calibrate? Simply warming up the probe, and using the STORED calibration works just fine for some measurements, but for the most accurate readings possible, calibration is suggested.

B) The DO Probe can be left soaking in water with the filling solution still in the electrode for several days. For long-term storage, however, the filling solution should be removed and the probe stored dry.

C) If you have carefully calibrated the Dissolved Oxygen Probe and you still fail to get good readings, check the integrity of the membrane cap. Inspect the cap for holes or tears in the membrane. Also, check to make sure that the membrane has not become clogged with dirt and oil. If you hold it up to a light, you should be able to see if it is dirty. If you are not sure, switch out the caps and see if that fixes the problem.

D) If you have tried everything and your DO Probe is still not behaving properly, please call Forston Labs Technical Support.

TN DO03 [Do you sell the DO Calibration Solution (sodium sulfite)?]

Yes, the DO Calibration Solution (sodium sulfite) can be purchased.

TN EA01 [Electrode Amplifier Troubleshooting and FAQs]

TROUBLESHOOTING

Primary Test: Connect an ORP sensor or a pH sensor to the Electrode Amp and connect the Electrode Amp to a LabPro. Start the data-collection program. Place the ORP or pH sensor in a buffer solution of known pH and confirm that the readings are within range.

Secondary Test: Confirm that the BNC connection is secure.

SPECIFICATIONS

Power = 7 mA @ 5VDC
Input range = -450mV to +1100 mV
Impedance > 100M Ohm
Gain: 2.2 V/V
Offset: 1.20 V (nominal)

CALIBRATION

Calibrate? Normally, yes. However, it depends on the sensor that is connected. The Electrode Amplifier amplifies the voltage produced by an electrode into a range where it can be monitored by the lab interface.

The Electrode Amplifier will report values in units of millivolts. If a pH electrode is attached, however, you can choose to read in units of pH. Custom, linear 2-point calibrations can also be performed if desired.

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Frequently Asked Questions (FAQs) - Tech Notes