The density of gas can be measured by using a scale!
Fill a container with gas and weigh it, then use a vacuum pump to evacuate the container, then weigh the container again.
The difference in weight is the weight of the gas.
You do the Mass of the object then, divide the Volume away from it.
Density = Mass / Volume. There is not an instrument that will measure both so you will need to measure them separately and calculate the density.
A seismometer is the instrument that measures the density of an earthquake, which is done by detecting and recording the vibrations produced by seismic waves. These measurements help scientists determine the magnitude and intensity of an earthquake.
A seismograph records the intensity measured by the Ritcher Scale.
A very common instrument for the direct measurement of the density of a liquid is the hydrometer, which measures the volume displaced by an object of known mass. A common laboratory device for measuring fluid density is apycnometer; a related device for measuring the absolute density of a solid is a gas pycnometer. Another instrument used to determine the density of a liquidor a gas is the digital density meter - based on the oscillating U-tube principle.
An argon gas analyzer measures the purity of Argon gas. The analyzer can be used to determine the actual content of Argon gas in a specific sample.
Lactometerlactometer
A hydrometer is an instrument that measures the density of liquids. Auto batteries could be checked to see the strength of the acid in each cell before sealed batteries were made. I don't know of an instrument for solids or gases.
What measures density
you would use a scale to measure the mass and a beaker to measure the volume. i need another tool
A pyranometer is the instrument used for measuring the intensity of sunlight. It measures the total solar radiation flux density in watts per square meter.
The answer will depend on what characteristic of the object is being measured: its mass, volume, surface area, colour, density etc.