Measuring the B-Scan noise with the transducer disconnected from the Transceiver Unit
Low noise is a key factor for high quality and reliable measurements. The performance of the CS90 will always be limited by different noise sources. A high noise level will mask the echoes and make them difficult to read and interpret. The noise is measured while the CS90 operates in Passive mode with the transmit pulses disabled.
Prerequisites
The CS90 is installed as specified in this manual. All cables - except the transducer - are properly connected. Neither tools nor instruments are required.
Context
This task allows you to check the noise conditions. To measure the noise level, observe the value presented on the B-Scan page in the Element BITE (Element Built In Test Equipment) dialog box.
Note
This task must be done with the transducer cable disconnected from the Transceiver Unit.
Procedure
1 Open the Operation menu.
2 Set TX Power to Off.
3 Make the following preparations.
a At the bottom of the CS90 presentation, select a suitable presentation mode, and activate the Horizontal view.
b Set Frequency to 70 kHz.
c Set Range to 1500 m.
d Set Gain to 20.
The Gain setting has no effect on the noise measurement.
e Select BITE to open the BITE (Built-In Test Equipment) dialog box.
f Select Noise to open the page.
4 Open the Element BITE (Element Built-In Test Equipment) dialog box.
a Open the Setup menu.
b Select BITE to open the BITE (Built-In Test Equipment) dialog box.
c Select Processor to open the page.
d Select Element BITE to open the dialog box.
e Select the B-Scan tab to open the page.
f Select Element amplitude.
g Set Start sample to 400
h Set Sample range to 10,000
5 Make sure that the channels are uniform.
6 Record the noise value at the bottom of the B-Scan page.
Image
Result
Requirements Results
Maximum noise level (in dB) shown on the B-Scan page when the transduceris disconnected is -115 dB.
Maximum noise level measured on the B-Scan page:  

Date and signature:
Further requirements
If the noise level is higher than specified, you must check the reason(s) for this.
•  Check the grounding of the Transceiver Unit.
•  Verify that other electric equipment and/or machinery on board, such as cooling systems, hydraulic pumps, electric motors etc, do not influence on the noise reading. Switch off as much machinery as possible, especially electrical motors.
•  Check for interference from other hydroacoustic systems.
•  Check for environmental noise, such as other vessels in the vicinity or animal life.