This page defines the calibration constants used by the radiometer to calculate the atmospheric temperature and attenuation from the raw readings received from the radiometer front-end. It also gives access to the tip curve and cold-load calibration / verification routines built into the radiometer.
WARNING:
The page displays a table with the parameters actually set. Each parameter value is a hyper-link to a separate page which lets you change this parameter. This parameter change page shows the actual parameter setting either in an entry field or in a drop down box. You may change the parameter to the desired value and then click to the 'Submit' button to pass the changed value to the radiometer. The radiometer automatically returns to the setup page when the parameter has been changed. To cancel a parameter modification you already started, either use the 'Back' button of you web browser or click to the 'Setup' button on navigation bar. Both returns to the setup page without changing the parameter you edited.
The table below lists the settings provided by this page.
Channel 1/2/3 Calibration Constants
These calibration constants appear three times for each radiometer channel separately.
| Parameter Name | Description |
|---|---|
| Noise correction (b) | The basic calibration factor, calibrates the pulse count to atmospheric temperature calculation. The noise correction factor usually is determined by a cold-load calibration. The cold-load calibration procedure built into the radiometer's software sets this value automatically when operator accepts the calibration result. |
| RX Reflection coeff. (r_ant) | The antenna reflection coefficient (equation 5.6) |
| Diplexer loss (L_wg1) | The wave guide / diplexer loss (equation 5.8) |
| W/G & coupler loss (L_wg2) | The waveguide / coupler loss (equation 5.7) |
| Waveguide loss (L_wg3) | The (external) wave guide loss to the cold-load (equation 5.20) |
| Waveguide loss (L_wg4) | The (external) wave guide loss to the cold-load (equation 5.19) |
| Test port W/G loss (L_wg5) | The test-port wave guide loss (equation 5.18) |
| Feed weight factor (a) | The feed weight factor for correcting the feed horn noise (equations 5.9, 5.10) |
| Feed loss (L_h) | The feed loss factor (equation 5.9) |
| Reflector loss (L_rfl) | The reflector loss factor (equation 5.12) |
| Media temperature | The media temperature used to calculate atmospheric attenuation from temperature. |
Misc. Calibration Constants
| Parameter Name | Description |
|---|---|
| Ground temperature | The ground temperature |
| Cosmic temperature | The cosmic temperature |
| Noise quantum | The noise quantum injected with one pule of the noise diode. (equations 5.5, 5.6) |
Reference Load Temperature Control
The behavior of the reference load temperature control has heavy impact on the radiometer calibration and the stability / reproducibility of measurement results. This is the reason why these parameter have been located here rather than at the settings page with the other antenna temperature control parameters.
| Parameter Name | Description |
|---|---|
| Ref load target temp. | The target temperature of the reference load. A single channel radiometer compares this value to the reference load 1 temperature, a radiometer with more than one channel the temperature control uses the average of both reference load temperatures as actual value in the control loop. |
| Ref load loop P-factor | The P-factor of the PI closed loop temperature control. |
| Ref load loop I-factor | The I-factor of the PI closed loop temperature control. |
| Temp. diff. fault limit | If the target / actual values of the control loop differ by more than this limit, a reference load temperature control fault is signaled. |
Tip Curve Calibration
The settings in this section define the parameters of a tip curve calibration / verification. For a detailed description of the tip curve calibration procedure see section Tip Curve Calibration .
| Parameter Name | Description |
|---|---|
| T/C minimum elevation | The minimum elevation angle to be set during the tip curve calibration. |
| T/C maximum elevation | The maximum elevation angle to be set during the tip curve calibration. |
| T/C number of steps | The number of (elevation) steps to be done during the tip curve calibration. |
| T/C measurement delay | The time to wait after moving the antenna to the first measurement sample. |
| T/C samples to average | The number of measurements sample to average at one elevation setting. |
| Start tip curve calibration | Clicking to this link lets the radiometer immediately start a tip curve measurement. |
Cold-Load Calibration
The settings in this section define the parameters of a cold-load calibration / verification. For a detailed description of the cold-load calibration procedure see section Cold-Load Calibration .
| Parameter Name | Description |
|---|---|
| C/L channel 1 nominal temp. | Enter the nominal temperature of the cold load here. This value usually is taken from the cold-load's data / calibration sheet. The value may depend on frequency. |
| C/L channel 2 nominal temp. | Enter the nominal temperature of the cold load here. This value usually is taken from the cold-load's data / calibration sheet. The value may depend on frequency. |
| C/L channel 3 nominal temp. | Enter the nominal temperature of the cold load here. This value usually is taken from the cold-load's data / calibration sheet. The value may depend on frequency. |
| C/L samples to average | The number of radiometer readings to be averaged for the calibration. |
| Switch channel 1 to cold-load | Starts a cold-load calibration for radiometer channel 1. |
| Switch channel 2/3 to cold-load | Starts a cold-load calibration for radiometer channel 2/3 |