# Example 21: corr_cond3 - conductivity corrections for RBRLegato and 6000dbar C and CT cell

With the RBR*legato³* C.T.D logger, the conductivity reading from the conductivity channel without corrections is given by a simple linear function:

where R is the normalized voltage ratio from the channel monitoring conductivity, **c0,c1** are the core coefficients of the linear equation, along with **c2** which is a geometrical factor (K-factor) reflecting the final installation of conductivity cell, and Craw is the uncorrected conductivity output, reported in mS/cm for RBR marine instruments.

The equation which corrects the output for the effects of both temperature and pressure on the conductivity cell is:

Casting the equation into the style used by the logger would give:

where

Craw is the uncorrected conductivity,

**c0**+**c1 × c2 × R,****x0**,**x1**correspond respectively to the temperature compensation constants "Kc1", "Kc2"**x2, x3, x4**correspond respectively to the pressure compensation constants "Kp1", "Kp2", "Kp3"**x5**is the calibration temperature "Tcal" in °C,**x6**is the calibration pressure "Pcal" in dbar,**n0**is the index of the internal temperature of the conductivity cell channel, in this example 7,

value(**n0**) is the final output value of the internal temperature of the conductivity cell channel in °C,**n1**is the index of the pressure channel, in this example 3,

value(**n1**) is the final output value of the pressure channel in dbar,Ccorr is the corrected output in mS/cm.

It is quite common to have a logger monitoring conductivity and temperature without a pressure channel, typically deployed at a known, constant depth. In this case, **n1** would be set to "**value**", and so value(**n1**) would be substituted by a default value (see the "**settings pressure**" command).

## Examples

```
>> calibration 1 type
<< calibration 1 type = cond13
```

Confirm the channel type.

`>> calibration 1 datetime = 20171201000000, c0 = 0.2346, c1 = 153.4873, c2 = 1.0001`

Set the core coefficients.

`>> >> calibration 1 datetime = 20171201000000, x0 = 0.2003, x1 = 0.2943, x2 = 0.005, x3 = 0.085, x4 = 0.0001, x5 = 15.0280, x6 = 10.0025`

Set the cross-channel correction coefficients.

```
>> calibration 1
<< calibration 1 type = cond13, datetime = 20171201000000, c0 = 0.2346, c1 = 153.4873, c2 = 1.0001 x0 = 0.2003, x1 = 0.2943, x2 = 0.0051, x3 = 0.0850, x4 = 0.0001, x5 = 15.0280, x6 = 10.0025, n0 = 7, n1 = 3
```

Request confirmation of all calibration coefficients.