複数の AM25T を
1つのデータロガーに接続
概要
AM25T 25チャンネル ソリッドステート マルチプレクサを使用すると、Campbell Scientific データロガーを使用して測定できる熱電対の数を増やすことができます。AM25Tはデータロガーとインターフェイスし、端子を追加して、追加の熱電対やその他の低レベル電圧出力センサを配線できるようにします。
続きを読む利点と特徴
- データロガーで測定できる熱電対の数が大幅に増加
- 最大 25個の熱電対を多重化
- 基準接点として機能するオンボード PRT を含む
- 複数の AM25T を 1つのデータロガーで制御できるため、測定できる熱電対の数が増える
- 金属製の内部グランドプレーンを使用して温度勾配を減らし、より正確な測定を保証する
- 垂直パッケージにより「設置面積」が小さくなり、混雑した収納箱に簡単に収まる
- 雷保護を使用する場合、最大 152.4m(500ft)のケーブル長をサポート
詳細
最大 25個の熱電対が AM25T の共通ディファレンシャルチャンネルに順番に接続されます。 (注意: データロガーのコモンモード範囲を超えないその他の低レベル電圧出力センサも測定できます。AM25T は抵抗ブリッジの測定に使用したり、AM25T とデータロガーの間に電圧分割器を構成したりしないでください。これらのアプリケーションについては、当社の AM16/32B マルチプレクサについてお問い合わせください。) このチャンネルからの出力は、データロガーのディファレンシャル入力チャンネルに配線されます。AM25T がチャンネルを順番に変更すると、データロガーは各熱電対からの出力を順番に測定します。
仕様
| 拡張性 |
|
| 内部PRT精度 |
|
| 電源 | 9.6～16 Vdc（負荷時）、非レギュレート |
| 通常のリレー抵抗 | 500 Ω |
| 最大スイッチング電流 | 25 mA (スイッチング電流が 25 mA を超えるとリレーが損傷し、使用できなくなります。) |
| CEコンプライアンス | EN55022-1:1995 および EN50082-1:1992 に準拠 |
| 動作温度範囲 |
|
| 寸法 | 23.6 x 5.1 x 13.2 cm (9.3 x 2 x 5.2 in.) |
| 重量 | 0.9 kg (2.0 lb) |
通常の消費電力 |
|
| 静止時 | 0.5 mA |
| アクティブ時 | 1.0 mA |
有効レベル |
|
| 非アクティブ | < 0.9 V |
| アクティブ | 3.5～5V |
クロック |
|
| レベル | スキャンの進行はクロックパルスの立ち下がりエッジで発生します （3.5 V以上から1.5 V以下へ） |
| 最小オン時間 | 50 µs |
| 最小オフ時間 | 60 μs |
互換性
注意： 以下は代表的な互換性情報を示しています。互換性のある製品や互換性のない製品をすべて網羅したリストではありません。
Data Loggers
| 製品 | 互換性 | 注意 |
|---|---|---|
| 21X (リタイア) | ||
| CR10 (リタイア) | ||
| CR1000 (リタイア) | ||
| CR1000X (リタイア) | ||
| CR10X (リタイア) | ||
| CR200X (リタイア) | ||
| CR206X (リタイア) | ||
| CR211X (リタイア) | ||
| CR216X (リタイア) | ||
| CR23X (リタイア) | ||
| CR295X (リタイア) | ||
| CR300 (リタイア) | ||
| CR3000 (リタイア) | ||
| CR310 | ||
| CR350 | ||
| CR500 (リタイア) | ||
| CR5000 (リタイア) | ||
| CR510 (リタイア) | ||
| CR6 | ||
| CR800 (リタイア) | ||
| CR850 (リタイア) | ||
| CR9000X (リタイア) |
互換性に関する追加情報
センサ
AM25T は通常、タイプ T、E、J、または K の熱電対で使用されますが、さまざまなタイプの熱電対もサポートされています (データロガーのモデルとオペレーティング システムによって異なります)。 AM25T は、低レベルの電圧出力を持つ他のセンサも測定できます。ただし、AM25T を抵抗ブリッジと一緒に使用したり、AM25T とデータロガーの間に電圧分割器を設定したりしないでください。これらのアプリケーションには、AM16/32B マルチプレクサを使用できます。
ソフトウェア/プログラミング
AM25T は、CRBasic の AM25T Instruction によって制御されます。Edlog を使用する場合、データロガー Instruction 134 は最近出荷されたバージョンのデータロガーで使用されます。古いデータロガーは、一連のデータロガー Instructionを使用して AM25T を測定および制御できます。
Short Cut ソフトウェア (当社の Web サイトから無料で入手可能) は、簡単なプログラミングをサポートし、AM25T アプリケーション用の配線図を生成します。Short Cut の古いバージョンは、マルチプレクサをサポートしていませんでした。
屋外収納ケースの考慮事項
AM25T は、ほとんどのフィールド条件で動作しますが、結露しない環境が必要です。屋外アプリケーションでは、乾燥剤で補強された耐候性屋外収納ケースが必要です。Campbell Scientific 屋外収納ケースが推奨されます。
ENC12/14 屋外収納ケースには、最大 2 台の AM25T、CR800、CR850、CR10X、CR1000、または CR3000、および電源装置を収容できます。ENC16/18 には、複数の AM25T、CR800、CR850、CR10X、CR1000、CR3000、または CR5000、および電源装置を収容できます。
よくある質問
AM25Tに関するよくある質問の数： 10
すべて展開すべて折りたたむ
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Bridge-type circuits (107/108 probes, PRTs, load cells, strain gages, and pressure transducers) should be used with the AM16/32(A or B) to preserve measurement accuracy and repeatability. Voltage signals (thermocouples, thermopiles, and high-level voltages) can be used with the AM25T multiplexer without any degradation to measurement accuracy or repeatability.
-
The AM25T was designed specifically to interface to Campbell Scientific data loggers only, with no provisions to interface to third-party devices.
-
The AM25T is typically used with thermocouples. It uses solid-state relays, which have a varying impedance from one closure to the next. This impedance is higher than the impedance in the mechanical relays used in the AM16/32-series multiplexer or the retired AM416 multiplexer. Bridge circuits (107/108 probes, PRTs, load cells, strain gages, and pressure transducers) should not be connected to the AM25T because of the varying and higher impedance values (compared to the AM16/32).
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The differences between the mechanical relays on the AM16/32B and the solid-state relays on the AM25T are noteworthy with regard to switching time, voltage and current levels, power consumption, and relay activation noise.
- Solid-state relays switch faster than mechanical relays. The solid-state relays on the AM25T have a maximum activation time of less than 1 ms, whereas the slower AM16/32B mechanical relays have a maximum activation of 20 ms. This is an important aspect to consider in high sample rate applications of a large number of channels.
- The mechanical relays on the AM16/32B multiplexer are rated for handling higher voltage and current levels than the solid-state relays on the AM25T.
- The power consumption for the mechanical relays on the AM16/32B multiplexer is significantly greater than that of the solid-state relays on the AM25T.
- The mechanical relays on the AM16/32B multiplexer make a distinct clicking sound when closing. In contrast, the solid-state relays on an AM25T are silent. The sound of mechanical relays may be annoying to humans or animals at the installation site. In some applications, the clicking sound of the relays can be a beneficial indicator that measurements are being performed.
-
The mechanical contact relays of the AM16/32B are subject to corrosion and pitting, which leads to increased relay resistance and greater variations of the resistance with each contact cycle. Switched currents in excess of 30 mA degrade the relay contacts involved, rendering the channel unsuitable for further low-level analog measurements. (If an AM16/32 relay has been used for currents greater than 30 mA, it is not suitable for low-level mV measurements.) The switching of higher level currents causes increased corrosion and pitting of the relays. The solid-state relays on the AM25T multiplexer are not subject to corrosion and pitting; therefore, they are more suitable for low-level mV signals.
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The number of switched lines and banks is different between the two multiplexers. The AM16/32B multiplexer has the operating option of running 16 banks of 4 lines each or of running 32 banks of 2 lines each. The AM25T multiplexer has only the one operating mode of 25 banks of 2 lines each. The 4x16 and 2x32 modes of the AM16/32B can offer more channels, convenience, and flexibility in applications than the 2x25-only mode of the AM25T multiplexer can. The 4x16 operation mode of the AM16/32B is a significant advantage for resistive bridge measurements to switch the current to the bridge circuits in addition to lines set up for the bridge output voltage. The 2x32 mode of the AM16/32B and the 2x25 mode of the AM25T multiplexer are commonly used for sensors that require no excitation (that is, voltages and thermocouples). In the 2x32 mode, the AM16/32B multiplexer has seven more channels than the AM25T offers.
-
Programming the AM25T multiplexer might be considered more convenient because the newer data loggers have a built-in AM25T CRBasic instruction to handle both AM25T differential thermocouple measurements and differential voltage measurements. There is no CRBasic built-in instruction for the AM16/32B multiplexer. However, the newer versions of the Short Cut program builder software have AM16/32B compatibility for a variety of different sensor types.
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The mechanical relays on the AM16/32B are subject to wear and thus have a limited lifetime. The minimum life rating of the AM16/32B relays is 107 closures. For a relay cycle interval of 1 second, the minimum lifetime is three years. The solid-state relays on an AM25T don't have this issue.
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The AM25T multiplexer has a built-in PRT temperature bridge circuit for accurate thermocouple cold junction compensation. It also has heat stabilization features designed to minimize temperature gradients across the wiring panel. The AM25T incorporates a large amount of thermal mass in a central concentrated area around the wiring panel terminals. The wiring terminals on the AM25T are located close to each other and close to the heat stabilization mass.
On the AM16/32B multiplexer, the wiring panel terminals are spread out across a larger area and do not have the large thermal mass design around the terminals that the AM25T has. Part of the thermal mass includes a heat bar that runs under the wiring panel connectors of which the PRT reference element is coupled to. The PRT element is incorporated into a precision full bridge circuit and calibrated for accurate reference temperature readings. The AM16/32B multiplexer does not have a built-in reference temperature PRT and heat bar design. When using AM16/32B multiplexers for thermocouple measurements, an external reference temperature measurement will need to be provided.
Because of its built-in reference temperature circuit and thermal stabilization features, the AM25T multiplexer is more suitable for thermocouple measurements.
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The mechanical relays of the AM16/32B multiplexer are needed for switching excitation currents into resistive bridge measurement circuits. The solid-state relays of an AM25T multiplexer, in contrast, are not suitable for this. The switching relays on the AM16/32B multiplexer are mechanical and have an order of 0.1 ohm resistance. In contrast, the relays on the AM25T are solid state with an on resistance of approximately 500 ohm. The significant resistance of the solid-state relays is problematic for the precision excitation current needed for resistive bridge measurements.
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