--- title: "Density Sensors & Monitoring | Aethair" description: "Water density is the mass of water per unit volume, and it changes with the water's temperature and the salts dissolved in it. 2 sensors and monitors that…" url: https://aethair.io/parameters/density/ --- Measurements · Water Quality # Density Also known as density of water Water density is the mass of water per unit volume, and it changes with the water's temperature and the salts dissolved in it. [Schedule a call](https://calendly.com/d/ctdd-mkr-v9v/aethair-demo-website) [Configure Density Monitoring](https://aethair.io/build/?params=density) At a glance g/cm³ Water Quality 1 way to measure it - **Thiamis** 2 external instruments What it is ## What is water density monitoring? Water density is the mass of water per unit volume, and it changes with the water's temperature and the salts dissolved in it. On this platform it is one of the conductivity-family values a multiparameter water-quality instrument reports alongside conductivity, specific conductance, salinity, and TDS, rather than something measured on its own. Two instrument families in the sensor catalog report it. The [In-Situ Aqua TROLL](https://aethair.io/sensors/in-situ-water-quality-sondes/) conductivity loggers and sondes (the Aqua TROLL 100 and 200 CTD loggers and the Aqua TROLL 400, 500, and 600 multiparameter instruments) report density in g/cm³ with the rest of their conductivity set. The Level TROLL and BaroTROLL loggers and the RDO probes do not. The [Spectra Scientific Spectra Litmus](https://aethair.io/sensors/spectra-scientific-water-quality-sondes/) configurable sondes (Litmus 6 and Litmus 4) report it in g/L. How it is measured ## How Density Is Measured Both families are read by a [Thiamis](https://aethair.io/products/thiamis/) gateway over Modbus RS-485. An In-Situ instrument first reports its model and serial number, then its parameter registers are polled each interval; fixed instruments such as the Aqua TROLL 100 and 200 return a set list, while the Aqua TROLL 600 is scanned so that whichever smart sensors are installed are discovered automatically. The Spectra Litmus is polled over Modbus RS-485 at 9600 baud; because it is a configurable smart-sensor sonde, the values that return depend on the sensors fitted to that unit. The Spectra Litmus has since been withdrawn from the vendor's catalog in favor of resold YSI EXO sondes. An instrument on Thiamis 2 A third-party instrument connected to a Thiamis gateway, reporting into the same Environet account. ### Every device and option that measures Density 2 | Device / option | Type | Base platform | Measures | | - | - | - | - | | [In-Situ](https://aethair.io/sensors/in-situ-water-quality-sondes/) · Level TROLL 300, Level TROLL 400, Level TROLL 500… | Water Quality Sondes | Thiamis | Density [Dissolved Ammonia (NH₃)](https://aethair.io/parameters/ammonia/) [Ammonium (NH₄)](https://aethair.io/parameters/ammonium/) [Blue-Green Algae](https://aethair.io/parameters/bga/) [Chloride](https://aethair.io/parameters/chloride/) [Chlorophyll](https://aethair.io/parameters/chlorophyll/) [Conductivity](https://aethair.io/parameters/conductivity/) | | [Spectra Scientific](https://aethair.io/sensors/spectra-scientific-water-quality-sondes/) · Spectra Litmus 6, Spectra Litmus 4 | Water Quality Sondes | Thiamis | Density [Dissolved Ammonia (NH₃)](https://aethair.io/parameters/ammonia/) [Ammonium (NH₄)](https://aethair.io/parameters/ammonium/) [Blue-Green Algae](https://aethair.io/parameters/bga/) [Chloride](https://aethair.io/parameters/chloride/) [Chlorophyll](https://aethair.io/parameters/chlorophyll/) [Conductivity](https://aethair.io/parameters/conductivity/) | [Configure Density Monitoring](https://aethair.io/build/?params=density) Related ## More in Water Quality [Water Temperature](https://aethair.io/parameters/water_temperature/) [pH](https://aethair.io/parameters/ph/) [ORP](https://aethair.io/parameters/orp/) [Specific Conductance](https://aethair.io/parameters/specific_conductance/) [Salinity](https://aethair.io/parameters/salinity/) [TDS](https://aethair.io/parameters/tds/) [Turbidity](https://aethair.io/parameters/turbidity/) [Dissolved Oxygen](https://aethair.io/parameters/do/) [Chlorophyll](https://aethair.io/parameters/chlorophyll/) [Nitrate (NO₃)](https://aethair.io/parameters/nitrate/) [Ammonium (NH₄)](https://aethair.io/parameters/ammonium/) [Dissolved Ammonia (NH₃)](https://aethair.io/parameters/ammonia/) Questions ## Density FAQ Which instruments report water density? The In-Situ Aqua TROLL 100, 200, 400, 500, and 600, in g/cm³, and the Spectra Scientific Spectra Litmus 6 and Litmus 4 sondes, in g/L. Do the In-Situ level loggers report density? No. The Level TROLL and BaroTROLL loggers and the RDO probes do not; density comes with the conductivity set of the Aqua TROLL instruments. How do these instruments connect? Over Modbus RS-485 to a Thiamis gateway, which polls their registers each interval.