Data Harvest Smart Wireless Gas Pressure Sensors

Smart Wireless Gas Pressure Sensors Absolute Gas Pressure Range: 0 to 400 kPa

Product No. 1150

Differential Gas Pressure Range: ±25 kPa

Product No. 1151 Data Harvest Group Ltd.1 Eden Court, Leighton Buzzard, Beds, LU7 4FY Tel: 01525 373666, Fax: 01525 851638 e-mail: sales@data-harvest.co.uk or support@data-harvest.co.uk www.data-harvest.co.uk  Data Harvest. Freely photocopiable for use within the purchasers establishment

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Gas Pressure sensors Contents Introduction .......................................................................................................................................2 The Smart Wireless Gas Pressure sensors .........................................................................................3 Connecting the sensor to a computer ...............................................................................................3 Measurement procedure ..................................................................................................................5 The Differential Gas Pressure sensor .................................................................................................6 The Absolute Gas Pressure sensor.....................................................................................................7 Practical information .........................................................................................................................7 Specifications .....................................................................................................................................9 Battery ...............................................................................................................................................9 Updating the Firmware......................................................................................................................9 Hard Reset .......................................................................................................................................10 Investigations & best sensor recommendation ...............................................................................10 Boyle’s Law (Pressure vs. Volume) .............................................................................................11 Rate of Reaction between marble chips and hydrochloric acid.................................................13 Pressure in liquids ......................................................................................................................14 Limited warranty .............................................................................................................................14

Introduction The Smart Wireless Gas Pressure sensors are both USB and Bluetooth compatible. Using Bluetooth a sensor can wirelessly connect to mobile devices such tablets and mobile phones as well as desktop or laptop computers giving students the ability to run experiments independently without being tethered to a traditional data logger. See the EasySense2 user manual system requirements for further details.

There two types of Gas Pressure sensor 1.

The Absolute gas pressure sensor (Product No.1150) has one port that measures the total pressure on a system. When the single port is left open the sensor will measure atmospheric pressure. Measures gas pressure in the range 0 to 400 kPascals (kPa).

2.

The Differential gas pressure sensor (Product No. 1151) has two ports and gives an output relative to the difference in pressure between the two ports. If one port is left open the measurement will be relative to atmospheric value. Measures gas pressure in the range -25 to +25 kPascals (kPa).

The sensing element of these Gas Pressure sensors is the piezoresistive type. They make use of the piezoresistive properties of silicon that change resistance to the flow of current when a stress or strain is applied to it. The sensor’s electronics has temperature compensation to minimise the effect of ambient temperature changes on data.

The connector on the Pressure sensor is of a female Luer lock type open-flow style so there is no shut-off valve to stop the flow. The female hub has a thread which screws with a half turn into threads in a sleeve on a male Luer fitting. Luer lock couplings are a standardised system for making leak-free connections between two fittings e.g. female to male fitting.

Both sensors are supplied with a mini USB lead (1 m standard A to standard mini B).

The Absolute sensor (Product No.1150) is supplied with 100 mm of silicon tubing, 2 male and 1 female Luer connectors. The Differential sensor (Product No. 1151) is supplied with 2 x 100 mm of silicon tubing, 4 male and 2 female Luer connectors.

Female Luer nylon thread style to barb connector, to fit 3 mm (1/8”) ID tubing

Male Luer nylon lock ring to barb connector, to fit 3 mm (1/8”) ID tubing

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Gas Pressure sensors The Smart Wireless Gas Pressure sensors Status light

On/Off switch

Female Luer connector

USB input

Unique ID number

Charge the sensor fully before first use Use the USB lead supplied to connect the sensor either direct to a USB port on your computer* or to a USB mains charger that outputs 5 V at 500 mA or more. A full charge can take up to 4 hours. *Or a powered USB hub. Your computer should be turned on and not in sleep or standby mode or the battery may drain instead of charge.

Status Light

Indicates

No light

Sensor is Off. Short press the On/Off switch

Blue flashing

Sensor On and Bluetooth advertising

White flashing

Charging via USB mains charger or USB port

Green flashing

Communication with the EasySense2 software (via USB or Bluetooth) has been established.

Orange flashing

Recording data

Red flashing

Battery is low

To switch the sensor off: Press and hold down the On/Off switch for about 2 seconds until the white light is lit solidly then release.

If not communicating with the EasySense2 software the sensor will put itself to sleep after a period of about one hour of inactivity (blue LED flashing).

Connecting the sensor to a computer Bluetooth users: Do NOT pair devices (if paired the sensor will not be available to the EasySense2 software). Computers or devices will need to support Bluetooth Low Energy (BLE), for further information refer to the instructions provided for the EasySense2 software.

Install the EasySense2 software, if it is not already on your computer. For details of how to install and operate this app, please refer to the instructions provided for the EasySense2 software.

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Gas Pressure sensors If connecting via USB: This sensor can be used like a traditional data logger connected via USB. Step 1: Connect the Gas Pressure sensor to the computer’s USB port using the USB cable supplied. The computer will automatically detect a new device and install the drivers. The status light on the Gas Pressure sensor will flash white to show it is charging.

Step 2: Open the EasySense2 app.

The Devices icon will change to green to show the Gas Pressure sensor as connected.

The status light on the Gas Pressure sensor will flash green to indicate a connection is established.

If connecting via Bluetooth: Step 1: Short press the switch to turn the sensor on (blue LED will flash).

Step 2: Open the EasySense2 app.

Step 3: Select the red Devices icon.

Step 4: Select to connect to the sensor (the list will show the ID number printed on the sensor).

ID number

Connect

The Devices icon will alter to green and the status light on the sensor will flash green to indicate a connection has been established.

Click or tap on

to close the box.

When you have finished use of the sensor select the Devices icon and Disconnect.

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To add another data logger or smart wireless sensor USB devices will be added automatically.

For Bluetooth or Wi-Fi devices select the Devices icon (top left of screen) then the Connect button for the device from the list of those available.

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Gas Pressure sensors Troubleshooting If the sensor loses Bluetooth connection and will not reconnect try  

 

Closing and reopening the EasySense2 software.

Close the EasySense2 software. Switch the sensor Off and then On again (To switch off: Press and hold down the On/Off switch for about 2 seconds until the white light is lit solidly then release. To switch back on: Press the On/Off switch (blue LED will flash). Reopen the EasySense2 software.

If you are using a Bluetooth Smart USB Adaptor connected to your computer, unplug the adaptor, plug back in again and try to reconnect.

Hard reset the sensor and then try to reconnect, see page 10.

Measurement procedure To avoid unnecessary wear to the female Luer on the sensor, an extension piece can be made up and kept in place.

Insert and twist

Sensor with female Luer connector

Silicone tube supplied, cut to about 15 mm in length

Female Luer connector

Male Luer connector Extension piece

Insert and twist

Sensor with female Luer connector Male Luer connector

Connect female to a male Luer connector

Avoid connecting a syringe direct to the female connector on the sensor. Connect either to the female Luer of the extension piece or to a piece of plastic tube / male Luer connector.

Extension piece

Luer slip Syringe (sometimes called ‘Luer fitting’ syringes)

Sensor with female Luer connector

Sensor with female Luer connector

Insert and twist

Plastic tube connected to a syringe

Male Luer connector

Sensor with female Luer connector

Insert and twist

Plastic tubing with an internal diameter suitable for the 3.2 mm (1/8”) barb on the connector e.g. 3 mm

Male Luer connector

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Gas Pressure sensors The Differential Gas Pressure sensor This sensor has two ports available to allow for the application of pressure to either side of the diaphragm.

These sensors measure the difference between the pressures applied to these ports.

P2

P1

P1 – P2 = Differential Pressure

If both ports are left open to the atmosphere, the effect of atmospheric pressure will equal each other out and the difference between the ports will be zero.

If only one port is used, and the unused port is left open to the atmosphere, the sensor will measure pressures above or below atmospheric pressure i.e. gauge pressure. If the sensor shows a reading of 25 kPa (gauge), that is 25 kPa above atmospheric pressure. Since atmospheric pressure is approx. 101.3 kPa, the equivalent atmospheric pressure reading would be 25 + 101.3 = 126.3 kPa (absolute).

Silicon or PVC tubes connected to the 2 ports on the Differential pressure sensor

The maximum pressure between ports P1 to P2 that this sensor can tolerate without permanent damage is: 200 kPa 3-way Valve

Investigations that would traditionally use a manometer can utilise the Differential sensor. One port is connected to the ‘living’ chamber that holds the organisms. The other port is connected to a ‘non-living’ chamber which acts as a thermo barometer. CO2 given off by the respiring organisms is absorbed by the potassium hydroxide resulting in a change of pressure.

Empty metal cage Maggots in a metal cage

Filter paper wick in Potassium hydroxide solution

Filter paper wick in Potassium hydroxide solution

Investigating the uptake of oxygen by maggots

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Gas Pressure sensors

Bubbles will rise to the top of the loop

3-way valve (to push air bubbles out with a top up syringe)

Branch with leaves

The Absolute Gas Pressure sensor This Pressure sensor is used to measure absolute pressure - the actual gas pressure at the port with respect to zero.

The pressure is measured against a builtin internal vacuum reference. The sensor then produces an output voltage that varies with absolute pressure.

The sensor measures accurately between 20 to 400 kPa in a linear fashion. Values below 20 kPa are slightly non-linear and may be not so reliable.

If the port is left open to the atmosphere, the sensor will display the value for atmospheric pressure, also known as barometric pressure, which is pressure caused by the downward force of the Earth’s gravity pressing the air down on the Earth. The average pressure exerted at sea level by the atmosphere in Britain is 101.325 kPa (1 atmosphere).

The maximum pressure that this sensor can tolerate without permanent damage is 1600 kPa.

Practical information ±25 kPa Differential Pressure sensor

0 to 400 kPa Absolute Pressure sensor

Temperature compensated

from -40 to +125˚C

Temperature compensated

from -40 to +125˚C

Maximum error

5% over 0 to 85˚C

Maximum error

1.5% over 0 to 85˚C

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Gas Pressure sensors Exposure beyond the following limits may cause permanent damage or degradation of the sensor ±25 kPa Differential Pressure sensor

0 to 400 kPa Absolute Pressure sensor

Maximum burst pressure on any port and between the ports. Above this and the sensor will be damaged.

200 kPa

Maximum burst pressure.

Above this and the sensor will be damaged.

1600 kPa

Storage Temperature

-40˚C to 125˚C

Storage Temperature

-40˚C to 125˚C

Operating Temperature

-40˚C to 125˚C

Operating Temperature

-40˚C to 125˚C

Humidity

0 to 95% RH (noncondensing)

Humidity

0 to 95% RH (noncondensing)

 The barb on the Luer connectors supplied with the Gas Pressure sensors is will fit PVC or Silicon tubing with an internal diameter of 3 mm (1/8”).  A Gas Pressure Accessory Pack, Product No. 1149, is available which contains a selection of tubing elements and connectors which allow gas tight connections to these Gas Pressure sensors.  Only use these sensors to measure non-corrosive/non-ionic media such as air or dry gases.  These sensors are not suitable for use with flammable gases.  A small amount of petroleum or silicon jelly, glycerine or similar wiped on the male Luer end will make the plastic tube slide on more easily.  The vapour pressure of liquids can be monitored but do not allow liquid to enter the sensor.  Protect from the weather – keep the sensor dry.  The container used with the Pressure sensor must be suitable for the task and able to sustain the pressure. The type of container selected will depend on the investigation.  A non-flexible airtight container like a syringe could be used for quantitative investigations e.g. pressure vs. volume.  Gas contained in a system under pressure will try to find a way out. The longer the investigation lasts the more dominant the effect of any leaks will become - try to complete the investigation as quickly as it allows.  The sensor is not waterproof. It may be cleaned using a damp cloth. Do not immerse in water or detergent. Do not place the sensor in an environment in which high humidity levels are possible as this may result in damage or malfunction.

Units of Measurement Pressure is defined as force per unit area and the standard SI unit of pressure is the pascal (Pa).

The conversion from kPa to mBar is simply to multiply by 10. (1 kPascal = 10 millibar = 0.14504 psi).

1 Pascal = 1 Newton per square meter (1 N/m2).

Equivalent values for 1 atmosphere (atm) are = 101.325 kPa = 760 mm Hg = 29.92 in. of Hg (at 0 oC) = 14.70 psi = 1013 millibar.

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Gas Pressure sensors Specifications Connectivity: USB or Bluetooth Fastest logging speed: 40,000 samples per second [25 µs] 16 bit ADC Firmware upgradeable USB communication to PC: Full speed compliant Power specifications: 5 V at 500 mA Battery: rechargeable internal lithium-ion 3.7 V, 1300 mAh Weight of sensor only: approx. 80 g External dimensions: approx. height 33 mm x width 50 mm x length 98 mm

Bluetooth 

Bluetooth 4.2 low energy radio, single mode compliant



Transmit (TX) power: 0 dBm



Receiver (RX) sensitivity: - 90 dBm



Usable transmission range: up to 10 m in open air



Frequency Range: 2.402 to 2.480 GHz operation

Battery The sensor is fitted with a rechargeable lithium-ion battery. Whenever the sensor is connected to the USB port on the computer or to a USB mains charger (output 5 V at 500 mA or more), it will automatically re-charge the battery (LED status flashing white).

The adaptor will stay awake for 60 mins when Bluetooth advertising (LED status flashing blue).

Once connected to the EasySense2 software (LED status flashing green) the adaptor will stay awake until the battery loses charge.

To switch Off: Press and hold down the On/Off switch for about 2 seconds until the white light is lit solidly then release.

Lithium-ion batteries are ‘memory-free’ and prefer a partial rather than a full discharge. Constant partial discharges with frequent recharges will not cause any harm. Frequent full discharges should be avoided whenever possible. Ideally the sensor should be stored at about 40% or more charge.

The speed at which a lithium-ion battery will age is governed by both its storage temperature (preferably less than 40˚C) and state-of-charge. Eventually the battery will no longer deliver the stored energy and will need to be replaced. A fully charged battery that loses its charge quickly will demonstrate the need for replacement.

When this happens, contact Data Harvest.

Updating the Firmware Occasionally Data Harvest may release updated firmware which will contain improvements or new features.

Updates will be made available from the product specific page on the Data Harvest website.

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Gas Pressure sensors Hard Reset If the Gas Pressure sensor fails to respond to the computer carry out a hard reset.

If necessary attach the sensor to power. Press and hold down the On/Off button for at least 8 seconds until the status LED gives a flash of blue light then release.

Release when LED gives a flash of BLUE light

Press and hold down the On/Off button for at least 8 seconds

If the sensor still fails to respond contact Product Support at Data Harvest.

Please provide details of: 

The computer platform it is being used with and the EasySense2 software’s version number.



A description of the problem being encountered

If possible, telephone from a location where you can operate the sensor with the computer.

Investigations & best sensor recommendation The recommendations and values quoted are based on our experience in using these sensors.  Best,  Okay,  Not recommended (results are likely be outside of this sensor’s range or the resolution is not good enough).

Investigations

Differential ±25 kPa

Absolute 0 to 400 kPa

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Boyle’s law (Pressure vs. gas volume)

Add the Wireless Temperature sensor and investigate the empirical gas laws e.g. GayLussac’s law (Pressure vs. absolute temperature) e.g. approx.

10 - 30 kPa movement

Rate of chemical reaction e.g. 5 - 20 kPa movement (depends on quantity of chemicals)

Production of gases in enclosed atmosphere e.g. O2 - photosynthesis of an aquatic plant approx.

10 kPa movement

Rate of Respiration e.g. Germinating seeds approx. 10 kPa movement

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Gas Pressure sensors Yeast Fermentation e.g. Carbon dioxide production approx. 10 kPa movement

Rate of Transpiration e.g. Plant on a windy or sunny day approx. 10 kPa movement

Chest expansion e.g. With Breathing Rate belt - Product No. 3190 approx. 3 kPa movement

Depth gauge (Lower the end of PVC tube into water e.g. 10 cm depth = about 0.8 kPa)

Changes in air pressure e.g. Weather studies approx. 95 to 105 kPa

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Boyle’s Law (Pressure vs. Volume) Using the 400 kPa Absolute Gas Pressure sensor.



Connect a short piece (approx. 2 cm) of plastic tubing to the nozzle of a syringe e.g. 10 or 20 mls.



Move the syringe piston to the required volume mark before connecting to the Pressure sensor.



Connect the tubing to the port marked P1 on the Pressure sensor.



Start the EasySense2 software and connect to the Pressure sensor.



From Setup select the mode as Snapshot and select Prompt for value on each sample. Type in Volume as the name, enter the units to be used and close.



Select Start. Tap or click on Take Sample to record the pressure and then enter a syringe value into the dialogue box and Save Sample.



Push the syringe plunger in to decrease the volume by a regular amount e.g. every 1 ml, take a sample of the pressure and enter the volume each time.

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Repeat the above until either the value reaches near the top of the sensors range or it becomes too difficult to push.

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Tap or click on the Reading name below the graph area and select Volume to be displayed on the X-axis.

Tap or click on Default range and select Min to Max to rescale the graph.

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Gas Pressure sensors



Select Calculate, Add Series. Enter the name as 1/Volume, the number of decimal places as 5, 1/mls as the units, the formula as a/x, a = 1, the series for x = Volume then Apply.



Plot a graph of Pressure vs. 1/Volume.

Typical results: -

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Gas Pressure sensors Rate of Reaction between marble chips and hydrochloric acid The rate of a chemical reaction can be affected by concentration of reacting chemicals, temperature, particle size and catalysts. The progress of the reaction between calcium carbonate and hydrochloric acid can be monitored by the evolution of carbon dioxide, CaCO3 + 2HCl -> CaCl2 + H2O + CO2. The carbon dioxide produced will cause a pressure increase in a sealed container.

-3

0.5mol mol dm HCl -3 0.5 dm HCl

Syringe with needle through the rubber bung (needs to be a tight fit)

Pressure Sensor

Conical flask with marble chips



Assemble the apparatus as shown. The quantity of marble chips will depend upon the size of the flask i.e. in a 250 ml flask use about 5 g of large marble chips.

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The two chemicals need to be kept separate until you are ready to start logging. Place the rubber bung in the flask without the syringe attached (to release any pressure). Draw up 10 cm 3 of 0.5 mol dm-3 hydrochloric acid into the syringe and fix to the needle.



Start the EasySense2 software and connect to the Gas Pressure sensor. A smoother graph line will be obtained if you reduce the interval of logging e.g. open Setup and change the interval to 500 ms.



Select Start to begin logging and add the hydrochloric acid from the syringe to the flask.



To produce the control data, select Overlay in the software. Remove the rubber bung, rinse the marble chips, fill the syringe with 10 cm3 of distilled water and repeat.

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Gradient can be used to find the rate of reaction from the slope of the graph.

Hydrochloric acid

distilled water added

Control – using distilled water

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Gas Pressure sensors Pressure in liquids If you measure the pressure at the end of a long plastic tube forced underwater, you can indirectly measure depth. In this experiment we connected a length of tubing to the Pressure sensor, attached the tube to a meter rule, inserted the end of the tube underwater and took a snapshot reading as the rule/tube was lowered in 5 cm stages. The pressure reading should increase by approximately 8 kPa for every meter below the surface of the water.

Limited warranty For information about the terms of the product warranty, see the Data Harvest website at: https://dataharvest.co.uk/warranty.

Note: Data Harvest products are designed for educational use and are not intended for use in industrial, medical or commercial applications.

WEEE (Waste Electrical and Electronic Equipment) Legislation Data Harvest Group Ltd is fully compliant with WEEE legislation and is pleased to provide a disposal service for any of our products when their life expires. Simply return them to us clearly identified as ‘life expired’ and we will dispose of them for you.

FCC Details This device complies with Part 15 of the FCC Rules. Operation is subject to the following two conditions: (1) this device may not cause harmful interference, and (2) this device must accept any interference received, including interference that may cause undesired operation.

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