Collecting Data with the Blood Pressure Sensor
This sensor can be used with the following interfaces to collect data:
• Vernier LabQuestTM as a standalone device or with a computer
(Order Code BPS-BTA)
Here is the general procedure to follow when using the Blood Pressure Sensor:
The Vernier Blood Pressure Sensor is used to
1. Connect the Blood Pressure Sensor to the interface.
measure systemic arterial blood pressure in humans (non-invasively). When used with
® 3.4 or newer or Logger Lite® 1.3.1 or newer data-collection software, it
3. The software will identify the Blood Pressure Sensor and load a default data-
can measure arterial blood pressure and calculate both the systolic and diastolic blood
collection setup. You are now ready to collect data.
pressure using the oscillometric method.
The following is a partial list of activities and experiments that can be performed
This sensor can be used with an interface and the following data-collection software.
• Measure blood pressure before and after exercise.
• Logger Pro
This computer program is used with LabQuest, LabPro, or Go!Link.
• Measure blood pressure while sitting or standing.
• Logger Lite
This computer program is used with LabQuest, LabPro, or Go!Link.
• Compare blood pressure after voluntary isometric contractions (weight lifting)
National Instruments LabVIEW™ software is a graphical
and a rhythmic activity such as running or biking.
programming language sold by National Instruments. It is used with SensorDAQ
and can be used with a number of other Vernier interfaces. See
Investigate how digestion affects blood pressure.
www.vernier.com/labview for more information.
Study the effect of caffeine on blood pressure.
• Compare blood pressure between smokers and non-smokers.
This product is to be used for educational purposes only. It is not
appropriate for industrial, medical, research, or commercial applications.
What is included with the Blood Pressure Sensor?
Using the Blood Pressure Sensor with a Computer
• Standard adult size adjustable cuff (27 cm to 39 cm)
When performing blood pressure measurements, it is best to work with a partner.
Currently, Logger Lite only supports blood pressure measurements in mm Hg.
Follow these general procedures to use the Blood Pressure Sensor with a computer:
• Blood Pressure Sensor booklet (this booklet)
1. Connect the Blood Pressure Sensor to Channel 1 on the LabPro or to a Go! Link.
How the Blood Pressure Sensor Works
Attach the rubber hose from the cuff to the connector on the sensor.
The active sensor in this unit is the SenSym SDX05D4 pressure transducer. It has a
2. Wrap the cuff firmly around your partner’s arm,
membrane which flexes as pressure changes. This sensor is arranged to measure
approximately 2 cm above the elbow. The two rubber hoses
differential pressure. The sensor produces an output voltage which varies with the
from the cuff should be positioned over the bicep muscle
pressure measured in the cuff. It includes special circuitry to minimize errors caused
(brachial artery) and not under the arm. Important: The
by changes in temperature. We provide an amplifier circuit that conditions the signal
person having his or her blood pressure measured must
from the pressure transducer. With this circuit, the output voltage from the Blood
remain still during data collection—no movement of the arm
Pressure Sensor will be linear with respect to pressure.
3. Start Logger Pro
(version 3.4 or newer) or Logger Lite
This sensor is equipped with circuitry that supports auto-ID. When used with
LabQuest, LabPro, Go! Link, or SensorDAQ, the data-collection software identifies
4. Logger Pro
or Logger Lite will identify the Blood Pressure
the sensor and uses pre-defined parameters to configure an experiment appropriate
Sensor and load the proper calibration. You are now ready to
6. Quickly and repeatedly squeeze the bulb to inflate the cuff on your partner’s arm.
Continue inflating the cuff to a pressure between 150 and 170 mm Hg. A meter in
Adjusting the Pressure Release Valve
the data-collection software will display the live pressure readings from the
The pressure release valve is set to release at a rate of 3.0
sensor. When the maximum pressure is reached, set the bulb pump down onto the
mm Hg/second on an arm of 32 cm in circumference. For
table. The built-in pressure release valve will slowly deflate the cuff.
arms much larger or much smaller it may be necessary to
7. After the pressure drops to 50 mm Hg, click
adjust the valve so that the exhaust rate stays in the range of
software and press down on the pressure release valve to release any air left in the
2.0–4.0 mmHg/s. With the bulb in hand and the hose
cuff. If the pressure does not reach 50 mm Hg by the time data collection ends,
leading away from you, place a screwdriver into the metal
adjust the exhaust rate of the pressure release valve according to the directions
slot on the top of the release valve. To increase the rate of
listed under “Adjusting the Pressure Release Valve”.
exhaust, turn the screwdriver clockwise. To decrease the rate of exhaust, turn the screwdriver counter-clockwise. The larger a subject’s arm the slower the release
Blood pressure readings will differ from person to person and even between measurements on the same individual. Do not expect to receive the same
Calculating Blood Pressure (Oscillometric Method)
measurements each trial since there are many factors that cause a person’s blood
The oscillometric method is a non-invasive means of measuring blood pressure. It is
pressure to increase or decrease. Use the following tips to take accurate
based on the principle that blood pumped through the arteries by the heart causes the
arterial walls to flex. When a cuff (placed around the upper arm to occlude the
• The subject’s arm and hand must remain still during measurements.
brachial artery) is inflated and then slowly deflated at a constant rate, an arterial
pressure pulse forms. These pressure pulses pass from the arteries, through the arm,
Proper placement of the pressure cuff will increase the accuracy of your blood
pressure measurements. The rubber hoses from the cuff should exit over the brachial artery and 2 cm above the crease in the elbow.
When the artery is fully compressed, blood flow stops along with the pulsations. As
• For younger students a smaller cuff is available (18 cm to 27 cm). Our small
the pressure in the cuff is slowly decreased, the arterial blood pressure increases to
blood pressure cuff can be ordered separately: order code XSCUFF.
the point that blood is forced through the artery in short pulses. As the pressure in
• Remove any clothing that may cover or constrict the portion of the arm being
the cuff continues to decrease, more blood flows through the occluded artery and the
pulses become increasingly significant until maximum amplitude is reached. Further
decrease of the cuff pressure minimizes the occlusion of the artery and the pulses
For most individuals it is not necessary to inflate the pressure cuff higher than
continue to decrease until the occlusion is removed.
170 mm Hg. Over inflation of the cuff may cause pain and/or injury.
• If the pressure release valve is exhausting slower or faster than
2.0–4.0 mmHg /s, then adjust the exhaust rate of the pressure valve.
Blood Pressure Sensor Specifications
Maximum pressure without permanent damage
These pressure pulses, when separated from the decaying mean pressure of the cuff,
form an oscillating waveform (see figure below). The peak-to-peak amplitudes of
this waveform create a bell shaped “envelope”. Within the envelope, the amplitudes of the waveform increase through the systolic blood pressure and continue increasing
until the mean arterial pressure (MAP) is reached. Physiologically, the cuff pressure
corresponding to the maximum amplitude approximates the mean arterial pressure.
Generally, the systolic blood pressure is calculated by determining the point along the envelope prior to the MAP using a known percentage of the maximum
amplitude. Diastolic blood pressure is calculated using the same method and the portion of the envelope following the MAP.
Oscillatory waveform used to create “Envelope”
Vernier warrants this product to be free from defects in materials and workmanship
for a period of five years from the date of shipment to the customer. This warranty does not cover damage to the product caused by abuse or improper use.
Vernier Software & Technology
13979 S.W. Millikan Way • Beaverton, OR 97005-2886
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, Logger Lite, Vernier LabQuest, Vernier LabPro, Go! Link, Vernier EasyLink and other marks shown are our trademarks or registered trademarks in the United States. CBL 2 and CBL, TI-GRAPH LINK, and TI Connect are trademarks of Texas Instruments. All other marks not owned by us that appear herein are the property of their respective owners, who may or may not be affiliated with, connected to, or sponsored by us.
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