PCB LARSON DAVIS CAL1250 (01) PDF DOCUMENT

If the PCB LARSON DAVIS CAL1250 equipment is used in a manner not specified by Larson Davis, the protection provided by the equipment may be impaired.

The PCB LARSON DAVIS CAL1250 Sound Level Calibrator has the following features:

• Meets CLASS 1 Acoustic Calibrator specifications

• OLED display

• Internal temperature, humidity, and static pressure sensors

• Dual output levels: 94.0 dB and 114.0 dB (user selectable)

• Dual output frequency: 250 Hz and 1 kHz (user selectable)

• Internal rechargeable lithium-ion battery (user-replaceable)

• USB-C charge port

• Swappable microphone adapter

The original packaging for the PCB LARSON DAVIS CAL1250 Calibrator will include the following:

• CAL1250 Sound Level Calibrator

• Protective Carrying Case (CCS064)

• Adapter for use with 1″ microphones (ADP117)

• Adapter for use with 1/2” microphones (pre-installed on calibrator) (ADP118)

• Adapter for use with 1/4″ microphones (ADP119)

• USB-C to USB-C cable and USB-A to USB-C adapter (CBL242-03)

• Calibration Certificate (CER-CAL1250)

The following accessories are available separately for the PCB LARSON DAVIS CAL1250:

• Adapter for use with 1/8″ microphones (ADP120)

• Adapter for use with 3/8″ microphones (ADP121)

The PCB LARSON DAVIS CAL1250 is shipped with the internal lithium-ion battery charged to about 50%. It is recommended to charge the unit to full before first-time use. A full charge takes approximately 3.5 hours.

1. Using the provided USB-C cable (and USB adapter if necessary), connect one end of the USB-C cable into the USB-C port on the side of the CAL1250, and the other end to an appropriate power supply (5 V, > 500 mA).

2. The calibrator will power on when connected to power, but will not produce a tone unless un-muted by pressing the “dB” button.

3. While charging, the calibrator will show a battery-charging animation in the top-right corner of the display. When fully charged, the battery animation will be replaced with a lightning bolt icon.

4. If the unit powers off while charging, the display will briefly show a large battery icon with a lightning bolt in the center to indicate the unit is still charging.

The battery will slowly discharge over time, even while the unit is off. If the unit is left unused for an extended period of time (several months), it may be necessary to recharge the battery.

The PCB LARSON DAVIS CAL1250 has four buttons: Power, Hz, dB, and Info.

Powering On/Off: Briefly push the power button to turn the calibrator on. Repeat to turn it off.

Operation: When powered on, the calibrator automatically begins emitting a tone. The active level/frequency combination when the calibrator is powered off will remain the active combination when powered on again.

Changing Level: Toggle the level between 114.0 dB and 94.0 dB by briefly pushing the “dB” button.

Changing Frequency: Toggle the frequency between 1000 Hz and 250 Hz by briefly pushing the “Hz” button.

Normal vs. Infinite Mode:

• In Normal Mode, the calibrator will power on for 120 seconds before shutting down. This countdown is shown in the upper left corner of the display. Any button press resets the countdown to 120 seconds.

• To switch to “Infinite Mode,” hold the “dB” button for several seconds. In this mode, the calibrator emits a tone until the user turns it off or the battery dies. The countdown timer is replaced by an “infinity” symbol (∞).

Display Pages:

• Default Page: Shows the calibrator frequency, level, and microphone coupling status. A filled circular icon below the battery status icon indicates the microphone is coupled; an empty circle means it is decoupled.

• Sensor Page: Press and release the “Info” button (“i” with a circle around it) to see temperature, humidity, and static pressure. Press and hold the “Info” button to change between Celsius and Fahrenheit.

• About Page: Press and hold the “Hz” button to see the device serial number, firmware version, manufacture date, and hardware revision.

To return to the default page from the Sensor or About page, tap the “Hz”, “dB”, or “Info” button.

When connected to power over USB, the calibrator will power on with the tone muted. It can be un-muted by briefly pressing the “dB” button.

The PCB LARSON DAVIS CAL1250 requires a microphone adapter, which can be changed to match the required microphone size.

• For 1″ microphones, use the ADP117.

• For 1/2″ microphones, use the ADP118.

• For 1/4″ microphones, use the ADP119.

To remove the installed adapter:

1. Grip the outer ring of the adapter.

2. Turn it a quarter turn counter-clockwise (when looking into the calibrator chamber).

3. Pull the adapter out of the chamber.

To install an adapter:

1. Ensure that the calibrator chamber and adapter are free from debris and dirt.

2. Insert the adapter into the calibrator chamber, lining it up until it seats properly.

3. Rotate the adapter a quarter turn clockwise to secure it in the chamber.

Before starting a calibration with the PCB LARSON DAVIS CAL1250, consider the following points:

• Allow the calibrator sufficient time to adjust to environmental conditions, especially temperature. This allows for more accurate calibrations.

• Ensure that the ambient noise level is sufficiently low for an accurate calibration. Calibration levels will be influenced by less than 0.015 dB for external noise levels lower than 89 dB for the 114.0 dB level and 69 dB for the 94.0 dB level.

• Ensure the microphone grid cap is installed securely before inserting the microphone into the calibrator chamber to avoid microphone damage.

• Ensure the proper microphone adapter is installed on the calibrator.

• When the CAL1250 battery is too low for a calibration, a “Low Battery” symbol will flash on the display a few times and the unit will not power on.

• It is good practice to perform a calibration check and any necessary adjustments of the instrument before beginning a sequence of measurements. At the end of the measurement sequence, the calibration should be checked again.

Step 1. Power on the calibrator and select the appropriate level and frequency.

Step 2. Insert the microphone into the calibrator chamber. Ensure they fit together securely. WARNING! Ensure the microphone’s grid cap is installed before inserting the microphone into the calibrator. Failure to do so may result in microphone damage.

Step 3. Allow time for the calibrator to stabilize, typically less than 10 seconds. The calibrator is stable when the “dB” indicator on the display stops flashing.

Step 4. Fix the arrangement vertically. The preferred method for calibrating is to mount the preamplifier in a fixed, vertical position. If this is not possible, laying the arrangement on a flat surface is preferred to holding the arrangement by hand. Initiate the calibration on the instrument and wait for it to complete.

Step 5. To verify the calibration was successful, take a measurement while the calibrator is still active. If the reading is not within tolerance, try recalibrating, or refer to the instrument’s manual for instructions on how to adjust the instrument.

The level measured by a microphone in an acoustic calibrator can be affected by the microphone’s construction. To calculate the corrected calibrator level, you must take the certified level from your calibrator and add the correction for your specific microphone model.

Level Seen By Meter = Certified Calibrator Level + Correction Value

Example:

A user wants to calibrate their sound level meter at 114 dB and 1000 Hz. The user’s calibrator is certified to 114.03 dB at 1000 Hz. They are using a 377B02 Free-Field Microphone on their meter. At 1000 Hz, the correction from the table for the 377B02 is -0.12 dB.

114.03 dB + (-0.12 dB) = 113.91 dB.

So, the user would set the calibration level in their sound level meter to 113.91 dB, instead of 114.0 dB.

The following table provides typical correction values for microphones manufactured by PCB Piezotronics and Larson Davis.

The certificate included with a microphone typically has correction values for 251.2 Hz and 1000 Hz. These values can be used to calculate the free-field to pressure correction for the microphone.

Correction Value = (1000 Hz Certification in dB) – (251.2 Hz Certification in dB)

Example:

A certificate for a 377B02 microphone shows the actuator value at 251.2 Hz is 0.00 dB and at 1000 Hz is -0.06 dB.

Correction Value = (-0.06 dB @ 1000 Hz) – (0.00 dB @ 251.2 Hz) = -0.06 dB

This calculated value is then used with the calibrator’s certified level to find the final setting for the sound level meter.

It is strongly recommended that a history of each calibration adjustment be kept for each piece of equipment. Normally, most modern equipment requires little or no adjustment once the initial calibration is performed. Systematic drifts are possible, and these should be recorded for corrective action.

Most Larson Davis sound level meters keep a history of each calibration change that can be retrieved.

While the PCB LARSON DAVIS CAL1250 will perform normally under a wide variety of gradually changing environmental conditions, some precautions should be taken when sudden changes occur:

• Temperature: The temperature of the CAL1250 should be stable. If the temperature changes suddenly, such as moving between indoor and outdoor environments, allow at least 15 minutes, or more optimally, 45 minutes for the calibrator to adjust. This will ensure that the temperature compensation sensors are at the same temperature as the rest of the unit.

• Humidity: While the CAL1250 is not adversely impacted by humidity, avoid environments that promote condensation. Avoid settings where the relative humidity exceeds 90%, as condensation is likely to occur.

• Electromagnetic Fields: The CAL1250 is effectively immune to electric or magnetic fields. However, the instrument being calibrated may not be. Therefore, calibration should not be done near motors, dynamos, high voltage wires, or other sources of electromagnetic fields.

The American National Standards Institute states, “An acoustical calibrator should be recalibrated at least annually by the instrument manufacturer or an acoustical test laboratory qualified to perform calibration.” (ANSI S1.40, 2006, par. 5.2)

If the CAL1250 is being used to calibrate several instruments, then the history of calibration adjustments can usually pinpoint which instrument is drifting. If all the measurement instruments are drifting in the same direction by an amount considered significant, the CAL1250 should be re-certified.

If the calibrator is behaving erratically, a hardware power-off may resolve the issue. This can be done by holding the power button for about 20 seconds.

The calibrator may also display an Error Code. While the error code is displayed, pressing any button will return the device to normal operation. Rebooting the device is often the best way to see the error code again.

Error Codes:

The PCB LARSON DAVIS CAL1250 can be connected to G4 LD Utility in order to read and update the firmware version.

1. Using a USB-C cable, connect the calibrator to a computer and open G4 LD Utility.

2. Click on the calibrator (listed as CAL1250 XXXXX) under the “Meters” panel on the left side of the window to see a range of information about the calibrator including the firmware version.

3. To update the firmware, click on the three dots (“…”), then click on “Upgrade Firmware”.

4. A dialog box will open, and the newest firmware version should be selected automatically.

5. Click “Upgrade Firmware” and wait for the process to complete.

The PCB LARSON DAVIS CAL1250 comes with a rechargeable lithium-ion battery. It is recommended that you use only a lithium-ion battery approved by Larson Davis. The battery should be replaced after 500 charge cycles or 3 years, whichever comes first.

NOTE: If the CAL1250 battery is deeply discharged, pressing the power button may have no effect. In this situation, the unit may need to be charged via USB for 15-30 minutes before it will turn on. After plugging into USB, the CAL1250 should flash a battery symbol on the screen before turning the screen off while a battery charge recovery occurs.

To replace the battery:

Step 1. Remove the screw in the battery door.

Step 2. Slide the battery door up away from the rest of the calibrator to remove it.

Step 3. Gently pull the existing battery from the battery terminals.

Step 4. Insert the replacement battery into terminals, ensuring proper polarity. If the battery is inserted backwards, the calibrator will not power on unless connected to power over USB. When connected to USB, the calibrator will assume the battery is dead and attempt to charge it, but a reversed battery cannot be charged. A reversed battery will not cause damage to the calibrator.

Step 5. Slide the battery door back into place, and re-attach the screw to secure it in place.

In most circumstances, wiping down the PCB LARSON DAVIS CAL1250 with a damp microfiber cloth is sufficient for cleaning. If desired, isopropanol can be used instead of water. DO NOT submerge the calibrator in liquids. If the chamber of the calibrator needs to be cleaned, take care not to allow any liquids through the vent holes onto the speaker.

The PCB LARSON DAVIS CAL1250 sound level calibrator complies with the following international standards:

The PCB LARSON DAVIS CAL1250 has the following microphone compatibilities:

According to IEC 61094-4:1995:

• 1″ WS1P, WS1F and WS1D microphones with ADP117 adapter.

• 1/2″ WS2P, WS2F and WS2D microphones with ADP118 adapter.

• 1/4″ WS3P, WS3F and WS3D microphones with ADP119 adapter.

According to IEC 61094-1:2000:

• 1″ LS1P with ADP117 adapter

• 1/2″ LS2P with ADP118 adapter