Outer jaws are used. Inner jaws will be use to find the inner dia of the cylindrical vessel.
To measure a hot water cylinder, you typically need to measure its height and diameter. Use a tape measure to determine the height from the floor to the top of the cylinder and the diameter across the widest part. These measurements will help determine the cylinder's capacity and size for replacement or installation purposes.
A vernier caliper
A caliper can be used to measure the internal and external diameter of a tube with about a 5cm bore. Make sure to use the appropriate jaws of the caliper for accurate measurements. Alternatively, a micrometer can also be used for precise measurements of the tube's diameter.
Vernier calipers are used to measure lengths with high precision, especially in applications where accuracy is critical. They consist of a main scale and a sliding vernier scale, allowing for measurements to be taken to a fraction of the smallest division on the main scale. They are commonly used in engineering, woodworking, metalworking, and scientific experiments.
Calipers measure the internal or external dimensions of something.
If you have a physical cylinder to measure, measure the "width" of the circle that is the cross section of the cylinder. That is the diameter, Half the diameter is the radius.
If you have calibrated eyeballs
A caliper is commonly used to measure the diameter of a copper wire. It can provide precise measurements by using its jaws to grasp the wire and providing a reading of the diameter on its scale.
External diameter, internal diameter, and tooth count.
A set of calipers.
To measure a hot water cylinder, you typically need to measure its height and diameter. Use a tape measure to determine the height from the floor to the top of the cylinder and the diameter across the widest part. These measurements will help determine the cylinder's capacity and size for replacement or installation purposes.
With a inside measuring micrometer
you measure across the top of the cylinder if it is a cylinder or across the circle if it is flat
A vernier caliper
Assuming it is a rod, the difficulty lies in that it can't measure the diameter of the beaker. Unless you were to attempt to find out the Radius/Diameter, then work out the circumference from that.
Callipers
Measure external diameter. (A) Measure internal diameter. (B) Subtract B from A