← ACARA Digital Technologies Years 9–10

Choosing a logging interval for sensor readings

How often a sensor records a reading. Short intervals give more detail but bigger files; long intervals save space but can miss fast changes.

Part of: ACARA Digital Technologies Years 9–10 — Acquiring and Validating Data — Module 35

Understanding Choosing a logging interval for sensor readings in ACARA Digital Technologies Years 9–10

What it does: Dividing the seconds in a day by the interval gives the number of readings. A smaller interval gives more readings, so more data to store. A long logging interval (every hour) saves space, but anything that changes quickly between readings is not recorded. Room temperature changes slowly, so a longer interval still shows the trend and keeps the file manageable. Short intervals give more readings, so you see more detail, but the file grows larger and uses more storage.

Common mistakes: The interval is a number of seconds, so it must be stored as a number. In quotes it is text, and 3600 / interval would cause an error. It should be interval = 60. The number of readings in a day is the seconds in a day divided by the interval. Multiplying gives the wrong answer. It should be count = day / interval.

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This module's key terms are also in a printable crossword (Modules 255–329) and word search (Modules 226–329).

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Learning
Duo
A weather station logs the temperature once every hour. Which statement about its data is correct?
It captures every tiny change and uses huge storageIt uses little storage but could miss a quick change between readings
Matches
A 2-minute spike in temperature is logged every 1 hour, so every spike will be recorded.
↓
An hourly interval can miss a spike that starts and ends between two readings, so the spike may never appear in the data.
Applying
Meanings
Term
logging interval
Meaning
How often a sensor records a reading. Short intervals give more detail but bigger files; long intervals save space but can miss fast changes.
Practice
seconds_per_day = 24 * 60 * 60
Testing
Gaps
interval =
Check Answer
Spots
1interval = "60"
2per_hour = 3600 / interval

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Quick Questions

1. A weather station logs the temperature once every hour. Which statement about its data is correct?
A. It captures every tiny change and uses huge storage
B. It uses little storage but could miss a quick change between readings ✓
A long logging interval (every hour) saves space, but anything that changes quickly between readings is not recorded.
2. Which logging interval produces the BIGGEST file after one day?
A. Every 1 second ✓
B. Every 1 hour
Every second gives 86,400 readings per day. Every hour gives only 24, so the file is much smaller.
3. A student wants to record how fast a ball's temperature changes when dropped into ice water over 30 seconds. Which interval suits best?
A. Every 1 second ✓
B. Every 1 hour
The change happens quickly, so a short interval is needed to capture the detail. Hourly readings would miss it entirely.
4. A school wants to track the slow change in room temperature across a whole term while keeping the spreadsheet small. Which interval is more sensible?
A. Every 30 minutes ✓
B. Every 1 second
Room temperature changes slowly, so a longer interval still shows the trend and keeps the file manageable.
5. What is the logging interval?
A. How accurate a sensor's reading is
B. How often a sensor records a reading ✓
The logging interval is the time gap between recorded readings, such as every second or every hour. It is not about accuracy.

Match the Pairs

interval = 1 (seconds) → The sensor logs a reading every second, giving lots of detail but a very large file
interval = 3600 (seconds) → The sensor logs one reading per hour, saving space but possibly missing fast changes
A short logging interval gives more detail but creates a bigger file → readings_per_day = 86400 / interval
A long logging interval saves storage space because fewer readings are stored → readings_per_day = 24 / interval_hours
A 2-minute spike in temperature is logged every 1 hour, so every spike will be recorded. → An hourly interval can miss a spike that starts and ends between two readings, so the spike may never appear in the data.
Logging every second for a month is best because the file size does not matter. → File size does matter: a very short interval over a long period creates a huge dataset that takes up storage and is slow to process.

Key Term

logging interval
How often a sensor records a reading. Short intervals give more detail but bigger files; long intervals save space but can miss fast changes.

Fill in the Blanks

1. # Log one reading every hour interval = 3600
Hint: Type the number of seconds in one hour.
2. perDay = 86400 / interval
Hint: Type the operator that divides the seconds in a day by the interval to count readings.
3. interval = 10 logReading() sleep(interval)
Hint: Type the variable name that holds the seconds to wait between readings.
4. if interval > spike: print("Spike may be missed")
Hint: Type the comparison operator that checks if the interval is longer than the spike.
5. if size > limit: interval = interval * 2 print("Longer interval set")
Hint: Type the arithmetic operator that doubles the interval to save space.

Spot the Error

Question 1
A interval = "60"
B per_hour = 3600 / interval
C print(per_hour)
Line A — The interval is a number of seconds, so it must be stored as a number. In quotes it is text, and 3600 / interval would cause an error. It should be interval = 60.
Question 2
A interval = 1
B day = 86400
C count = day * interval
D print(count)
Line C — The number of readings in a day is the seconds in a day divided by the interval. Multiplying gives the wrong answer. It should be count = day / interval.
Question 3
A every_second = 3600
B every_hour = 24
C print(every_second > every_hour)
Line A — There are 86400 seconds in a day, so logging every second gives 86400 readings a day. 3600 is the number of seconds in an hour, not the number of readings in a day.
Question 4
A interval = 3600
B if interval > 60:
C print("Big file")
D else:
E print("Big file")
Line C — A long interval (over 60 seconds) means fewer readings, so the file is small. Line 3 should print "Small file".
Question 5
A # Heart rate sensor
B interval = 3600
C log_every(interval)
Line B — Heart rate changes quickly, so logging once an hour would miss most of the changes. A short interval such as 1 second is needed. It should be interval = 1.

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