16K-W-BB-55

オフィール社のセンサとディスプレイ/インターフェースは個別に校正されています。各ディスプレイ/インターフェースのアナログ出力精度は同じで、約0.2％程度でしかないのです。センサはディスプレイ/インターフェースとは別に、固体ごとにNIST準拠の基準器で校正され、校正情報はセンサ直属ケーブル先端にあるSHコネクタ内部のROMに記録されています。センサをディスプレイ/インターフェースに接続すると、ディスプレイ/インターフェースはセンサからの校正係数を読み込みます。オフィール社のセンサ単体での代表的な校正精度は+/-3%で、ディスプレイ/インターフェース単体での校正精度は約0.2％ですから、合成された校正精度は√(3のニ乗+0.2の二乗)となります。その変化分はほぼ考慮しなくてよい誤差範囲なので、センサはいずれのディスプレイ/インターフェースと接続することができます。

オフィールにおける校正精度は通常、標準偏差で2σでのものです。つまり、精度が +/-3%と記載されている場合、センサの95.4% のものはこの範囲に入り、99.7% のものは+/-4% の範囲に入ることを示します。校正精度については、別途お問合せください。参考： https://www.ophiropt.com/laser-measurement-instruments/laser-power-energy-meters/tutorial/calibration-procedure

パワーをP、ビーム径をD とすると、パワー密度はP /(.785 * D²) で計算されます。（.785=ビーム径φ1cmの時の面積）パルスレーザの場合、エネルギをE、繰返し応答周波数をR 、ビーム径をD とすると、パワー密度はE*R/(.785 * D²)で、エネルギ密度はE/(.785 * D²) で計算されます。※センサに入射する場合は、ビームモードを考慮してマージンをみてください。

流量と水圧については下記のグラフをご参考ください。

各水冷センサの最小水量、水温、水温変化についてはカタログ仕様をご確認ください。

注釈： 水冷却は最小水圧の2.5倍以上にはしないでください。2.5倍にしても規定の流量が流れない場合は、センサの水路が詰まっている可能性も考えられますので弊社までお問合せください。

30K-W水冷センサについては、こちらから仕様をご確認ください。

サーマルセンサのダメージスレッショルドは、パワー密度だけでなく、出力レベルに依存します。センサディスク自体が、ハイパワーが入射されると、より熱を吸収するからです。例えば、オフィール社のBB型コーティングを採用したセンサの場合、10W入射の場合は50kW/cm²ですが、300W入射の場合は10kW/cm²となります。オフィール社のダメージスレッショルドは、特定のセンサに対して最大パワーを入射した場合の値とされています。他の製造メーカのほとんどは、ここまでは行われていません。仕様を比較する場合、カタログ数値だけの比較ではなく、このような背景も考慮してください。

校正精度に影響する場合もありますので、パワーセンサ/エネルギセンサの詳しいクリーニング方法について、ご不明の方はお問合せください。

Absorber Type	Umicore #2 Substrate Cleaner	Acetone	Methanol	Umicore #2 + Acetone
Alumina
Thermal BB
Pyro BB
BF
Comet BB
EX
HD
HE
HE1
HL
LP
LP1
Pyro Metallic
P type
N type
UV
10K-W(Reflector)

These sensors have a gold-coated reflecting cone, which can be easily scratched. If one of these sensors needs to be cleaned, we recommend blowing with clean air or nitrogen. If, however, the cone gets soiled (for example with something spilled on it), such that blowing is not enough to clean it, then there is a risk of the contaminant material getting “burned in” by laser radiation. In such a case, to avoid that risk, one should use a suitably soft tissue with solvent, and wipe as gently as possible.

特に指定がない限り、オフィールのセンサー及びディスプレイは購入日から18か月以内に初回の校正を受けて頂く事をお勧め致します。その後は年次定期校正を受けて頂く事を推奨致します。

In theory, if a beam is completely parallel and fits within the aperture of a sensor, then it should make no difference at all what the distance is; it will be the same number of photons (ignoring absorption by the air, which is negligible except in the UV below 250nm). If, nevertheless, you do see such a distance dependence, there could be one of the following effects happening:

• If you are using a thermal type power sensor, you might actually be measuring heat from the laser itself; when very close to the laser, the thermal sensor might be “feeling” the laser’s own heat. That would not, however, continue to have an effect at more than a few cm distance unless the light source is weak and the heat source is strong.
• Beam geometry – The beam may not be parallel and may be diverging. Often, the lower intensity wings of the beam have greater divergence rate than the main portion of the beam. These may be missing the sensor's aperture as the distance increases. To check that you'd need to use a profiler, or perhaps a BeamTrack PPS (Power/Position/Size) sensor.
• If you are measuring pulse energies with a diffuser-based pyroelectric sensor: Some users find that when they start with the sensor right up close to the laser and move it away, the readings drop sharply (typically by some 6%) over the first few cm. This is likely caused by multiple reflections between the diffuser and the laser device, which at the closest distance might be causing an incorrectly high reading. You should back off from the source by at least some 5cm, more if the beam is not too divergent.

Needless to say, it’s also important to be sure to have a steady setup; a sensor held by hand could easily be moved around involuntarily, which could cause partial or complete missing of the sensor’s aperture at increasing distance, particularly for an invisible beam.

Corrosion is caused by interactions between the metallic components of the sensor and the cooling water, which may contain a variety of dissolved ions. Many factors affect the risk of corrosion forming, but the most important are the pH and the mixture of ions in the water. For this reason, we recommend using neutral deionized water in a closed circulating system (pH between 6 and 8). Please note that deionized water is usually slightly acidic (pH 5.65) due to absorption of CO2 from the atmosphere. The cooling water can be neutralized by adding 5 ml of a 10 mM solution of NaOH for each liter of water in the cooling system. Commercial additives such as Optishield Plus are also recommended for systems such as ours that have copper and aluminum in them. Optishield has the additional benefit of having biocide to prevent buildup of organic contamination.

To prevent corrosion it is also crucial to not allow standing water to evaporate inside the sensor when it is not in use. When disconnecting a sensor from the cooling system, the water channel should be cleared by blowing compressed air through it.

For those customers still experiencing problems with corrosion, we recommend the new thermal sensor 1000WP-BB-34 which has a special design in which all materials that come into contact with the cooling water are either copper or nonmetallic.

You can find a lot more information about the correct use of water-cooled sensors in the article "How to use water cooled Ophir sensors", here.

Many factors affect the risk of corrosion forming, but the two most important are:

• the mixture of ions in the water
• the water’s pH

Our current recommendation is to use DI water – but of a neutral pH. DI water is usually slightly acidic; it can be titrated to a neutral pH, using a bit of sodium hydroxide for example. There are also commercial additives that can help prevent corrosion, for instance Optishield Plus. For a more detailed discussion, see the FAQ at https://www.ophiropt.com/laser--measurement/knowledge-center/faq/7805

You can find a lot more information about the correct use of water-cooled sensors in the article "How to use water cooled Ophir sensors", here.

We don’t supply chillers, nor insist on specific models; the only important thing from our point of view is to simply keep to the requirements specified for the cooling water of the specific model of sensor, such as minimum flow rate at full power, water temperature range, and - more important than the actual water temperature - water temperature stability. The temperature of the water should not be changing by more than 1 deg/min (because changes in water temperature could cause heat flow in the sensor which would be detected as if it were laser power, and cause errors in the reading).

We also have a video on our site at https://www.ophiropt.com/laser-measurement-instruments/laser-power-energy-meters/knowledge-center/water-cooled-sensors-youtube, which discusses various issues and tips about water cooling. There is a short discussion of coolant pressure requirements in our FAQ section at https://www.ophiropt.com/laser--measurement/knowledge-center/faq/2404