CMA Dishmachines BT48i User manual

HEART RATE SENSOR BT48i
USER’S GUIDE
CENTRE FOR MICROCOMPUTER APPLICATIONS
https://www.cma-science.nl

2 | BT48i Heart Rate Sensor User’s Guide
Short description
The Heart rate sensor BT48i provides a simple way to study the heart's function.
Unlike an electrocardiograph (EKG), which monitors the electrical signal of the
heart, this sensor monitors the flow of blood through the veins.
The cardio clip consists of a small infrared LED, which illuminates the tissue and a
light sensitive detector, which detects the amount of light transmitted from the
tissue. !
As the heart forces blood through the blood
vessels, the amount of blood changes with time.
The sensor measures the light level transmitted
through the vascular tissue and the corresponding
variations in light intensities that occur as the
blood volume changes in the tissue. The
measured signal is amplified, inverted and
filtered. The sensor is equipped with an
amplification knob that allows amplifying the signal when it is too weak.
The Heart rate sensor can be directly connected to analog BT inputs of CMA
interfaces. The sensor cable BT - IEEE1394 needed to connect the sensor to an
interface is not supplied with the sensor and has to be purchased separately (Order
Code BTsc_1).
Measurement procedure
• Insert the jack plug from the cardio clip into the jack socket at the side of the
sensor box.
• Attach the clip to either the fingertip or to the ear lobe. You can also place the
clip on the web of skin between the thumb and index finger.
• Check if the recorded signal is strong enough. If this is not the case you may use
the amplification knob to amplify the signal.
• Stay still as any muscle movements will influence the signal.
• Wait until the signal stabilizes and start recording data.
The recorded pulse waves
show details of the pumping
action of the heart. Example of
a measurement is shown in the
figure. The blood flowing
through the earlobe rises at
the start of the heartbeat. This
is caused by the contraction of
the ventricles forcing blood
into the arteries. In the Coach
program you can determine

BT48i Heart Rate User’s Guide | 3
the heart rate by analyzing the time between peaks, or counting the number of
beats per minute by using the heart rate sensor as counter with a threshold of e.g.
35%.
Heart rate varies between individuals. At rest, an adult man has an average pulse of
72 per minute. Athletes normally have a lower heart rate than less active people.
Children have a higher heart rate (approx. 90 beats per minute), but also show
large variations. The heart rate rises during exercise and returns slowly to the rest
frequency after exercise. The rate at which the pulse returns to normal can be used
as an indication of fitness.
Notes:
• The Heart rate sensor cannot be used during exercises. The body’s movement
would cause shifting of the ear clip and erroneous readings.
• The ear and clip should be shaded from strong light.
• The Heart rate sensor is not appropriate for medical or research applications.
Specifically, it may not be used for patient diagnosis.
Sensor recognition
The Heart rate sensor has a memory chip (EEPROM) with information about the
sensor: its name, measured quantity, unit and calibration. Through a simple
protocol this information is read by the CMA interfaces and the sensor is
automatically recognized when it is connected to these interfaces.
If your Heart rate sensor is not automatically detected by an interface you have to
manually set up your sensor by selecting it from the Coach Sensor Library.
Calibration
The CMA Heart rate sensor BT48i is supplied calibrated. The output of the Heart
rate sensor is linear with respect to voltage. The supplied calibration function is:
I(%) = 20 * Vout(V)
The CMA Coach program allows selecting between the calibration supplied by the
sensor memory (EEPROM) or the calibration stored in the Coach Sensor Library.
Suggested experiments
• Measurements of the heart rate of different individuals.
• Measurements of the heart rate before and after exercises.
• Measurements of the recovery time: how fast a person's heart rate returns to
its normal performance after exercise.
• Measurements of the heart rate before and after drinking coffee (or Coca-Cola).
• Simultaneous measurements of heart rate, EKG and heart sounds with sound
sensor to register heart tones.

4 | BT48i Heart Rate Sensor User’s Guide
Technical Specifications
Sensor kind
Analog,
generates an output voltage between 0 and 5 V
Amplitude
Each heartbeat gives a peak. If the peak is less than
0.2 V the ear clip should be repositioned.
Resolution using
12- bits 5V AD converter
0.125%
Calibration function
I(%) = 20 * Vout(V)
DC-level
1.5 V
Frequency response
Band-pass filter 2.4 – 12 Hz
Supply voltage
Supply current
5 V DC
12 mA
Ear Clip
An infrared LED and a light sensor
Connection
IEEE1394 connector for BT-IEEE1394 sensor cable.
Sensor cable not delivered with the sensor.
Warranty:
The Heart rate sensor BT48i is warranted to be free from defects in materials and
workmanship for a period of 12 months from the date of purchase provided that it
has been used under normal laboratory conditions. This warranty does not apply if
the sensor has been damaged by accident or misuse.
Note: This product is to be used for educational purposes only. It is not appropriate
for industrial, medical, research, or commercial applications.
Rev. 19/05/2020