ACARA v9 CONTENT DESCRIPTION “follow procedures to make and record observations, including making formal measurements using familiar scaled instruments and using digital tools as appropriate”
Builds on earlier measuring with rulers and thermometers. Now you follow the steps of a measurement with two new instruments, a force meter and a rain gauge, reading each scale the right way and logging every reading with its unit so the record can be trusted and compared.
Following the steps of a measurement
A measurement is not a guess. It follows the same steps every time. First you pick the right instrument: a force meter, also called a spring scale, for how hard something is pulled, and a rain gauge for how much rain has fallen. Each instrument has a scale, which is a line of marks with numbers. You read the mark the pointer or the water lines up with, and you write down the number and its unit: newtons for a pull, millimetres for rainfall. Reading the scale level with your eye, straight on, keeps the number honest.
Read the scale: log force-meter pulls trial by trial
A toy wagon was pulled across a bench and the force meter was read in newtons each trial. Switch between the table and the chart to see the same logged readings two ways.
The table holds the exact newtons you read off the force meter each trial. The chart turns those same logged readings into a shape, and the steady climb shows the pull growing stronger as the load was made heavier.
Reading a scaled instrument correctly
A scaled instrument only gives the right answer if you read it the right way. On a force meter, a pointer slides past a line of numbers as you pull, and you read the mark the pointer rests on, in newtons, looking straight on. On a rain gauge, the rain settles at a line on the side, and you read that line in millimetres. Reading from above or below the mark makes the number look bigger or smaller than it really is, so you always get level with the scale first, then log the reading.
Record rainfall: a digital tool logs the daily readings
A rain gauge was read at the same hour each morning and the millimetres were logged. The bar chart and the line graph are two ways a digital tool can show your recorded readings.
Each bar is one reading you logged in millimetres from the rain gauge. A digital tool draws the chart for you from the records, but the readings themselves still came from reading the gauge carefully each morning.
Watching for a reading that does not fit
When you record a row of readings that should change smoothly, one number sometimes jumps far away from the rest. That odd reading is worth a second look. Perhaps the force meter pointer stuck, or the rain gauge was tipped, or you read the wrong line. A careful recorder does not rub it out and does not panic. You simply take that one measurement again, the same careful way, and see whether the strange reading was a slip.
Spot the force reading to measure again
The same wagon was pulled with heavier and heavier loads, and the force meter was read in newtons each time. The pulls should rise steadily, but one reading does not fit the climb.
Click the point that does not fit the pattern of the others.
Which records can you trust?
A measurement is only useful if it was made carefully and logged with its unit. Some records were taken the proper way, reading the scale level and noting the unit. Others were rushed, guessed, or written without a unit, so they cannot be trusted or compared. Sort each one by whether it is a careful, trustworthy record of the force-meter and rain-gauge measuring you set out to do.
Decide which records were measured carefully
The aim: make careful, trustworthy records of pulling force and rainfall. Decide which records meet that aim.
Claim: A good record gives an exact reading from the scale, with the matching unit, taken the careful way.
The wagon pull was read off the force meter as 6 N, looking straight on at the pointer.
The rain reached the 12 line on the gauge, so 12 mm was logged into the digital table.
The pull felt about medium, so nothing exact was written in the table.
The force meter pointer rested on the 9 mark and 9 N was recorded next to the unit.
A rainfall number was guessed from the window without reading the gauge up close.
Decide whether each statement is evidence for the claim, or not.
Why this matters
Careful measuring and recording is the backbone of every investigation. When you follow the steps, read a force meter or rain gauge the right way, and log each reading with its unit, your records can be checked, compared and trusted by anyone. It is the same care a meteorologist, an engineer or a scientist takes whenever a measurement has to be right.
Quick self-check
1. You measure how hard a wagon is pulled with a force meter. Which unit do you write down?
2. To read a force meter or a rain gauge correctly, where should your eye be?
3. Rain collects in a rain gauge overnight. Where do you read the amount?
4. Why log each force-meter reading into a digital tool as soon as you take it?
5. Your rain-gauge totals are 2 mm, 5 mm, 8 mm, then 1 mm, then 14 mm. What should you do with the 1 mm?