Nuclear Gauge Help, M Count D count

[Aethonle]

thread261-367840

Hi Everyone. I am currently working full time with nuclear gauge and observe a set of numbers on the screen. I know about the density and moisture but what is confusing is the M count and D count, which keeps changing with the Depth of Rod and with different Density and Moisture standards.

It disturbs me to keep repeating something of which I don't possess complete knowledge.

My question is, how are D count and M count Related to density, moisture, Density standard, Moisture standards, and depth of the source Rod.

I googled a lot but could not find a formula or any charts etc. This is the only thread someone has mentioned it on.

I shall be grateful for the help of experts.

Thank you very much.

 

[TigerGuy]

Almost everything is gauge specific. So, there is nothing published that will give you the formula and charts you are seeking.

First, have you been properly trained and certified to be handling and operating the unit? Some require more training than others, and I will assume you are either licensed or operating under the supervision of somebody that is.

Definitely check the operations manual for the unit you have.

For nuclear density gauges, such as the Troxler 3440, Instrotek 3500, etc: you need to perform a daily standard count. This daily count may need to be done more often depending on a number of factors.
This daily count should demonstrate that the unit is operating in a consistent manner.

When you are testing in the field, the unit will record specific values for the material being tested. The DC is often called the Density Count. On the Troxler, this is effectively the count of Gamma rays from the source that reach the counter in the opposite end of the unit. I don't think it's the actual, but it represents how much is getting through the material. There will be some variability to it, even if you run the test repeatedly in the same location. The source emits Gamma radiation. Every time the Gamma radiation hits something, it re-directs and is not detected by the counter. Remember, this is at the atomic level. There is a lot of space between the nucleus of adjacent atoms, so there will always be some Gamma radiation reaches the counter. The lower the number displayed for DC, the more solid mass (nucleus of atom) between the source and the counter. The unit will use this DC reading to calculate the Wet Density of the material being tested. It is entirely dependent on your unit, it's current daily standard counts, and the depth of the source rod for each test.

A second source is mounted in the base of the unit and emits neutrons. When these neutrons pass through the nucleus of a hydrogen atom, their dynamic properties change which is detected by the gauge. This will be indicated as your MC, or Moisture Count. The MC is used to calculate the Moisture present, again dependent on the individual unit and daily standard counts. Be aware, there are substances out there besides water that contain hydrogen.

Wet Density is calculated as a mass per unit volume (pounds per cubic foot, kilograms per cubic meter, etc). Moisture is presented as the mass of water in the same volume.

Wet Density - Water = Dry Density. (Water/Dry Density) x 100 = Percent Water

Your Dry Density and Percent Water is what is typically compared to the Moisture-Density curve to assess compaction characteristics of fill soil.

 

[Aethonle]

I am thankful for your response and for explaining the science behind the nuclear gauge and the density and moisture counts.

Also, what about the void ratio? Is that also gauge's internal calculation, or can we calculate that theoretically from other numbers we obtain?

 

[TigerGuy]

Your void ratio is based on the material's specific gravity. I've never seen a density report that uses the gauge's calculated void ratio.