FOXBORO FBM203輸入輸出模塊
傳感器安裝
11.1概述始終根據傳感器的工作情況安裝傳感器說明書
通常，用于比空氣輕的氣體的傳感器應位于高于空氣的氣體的高液位和傳感器應位于：低水平。
請勿安裝傳感器：
a、 其中正常氣流可能被阻礙。
b、 可能存在靜態氣穴的房間角落。
c、 靠近熱源，如對流加熱器。
務必安裝傳感器：
a、 盡可能靠近待檢測的潛在氣體源以便給出最大可能的警告。
b、 以便它們可用于維護工作。11.2傳感器線路電阻
傳感器的位置應確保電纜的線路電阻
不超過允許的最大值。該表提供了以下內容的快速指南：
特定傳感器允許的最大電纜長度，當通過各種尺寸的絞合銅導線電纜連接到系統57以最小直流輸入電壓運行。表中的數字為最大值提供了有用的參考指南
然而，在許多情況下，電纜長度較長可能被使用。例如，其中dc輸入電壓高于最小值。在里面在這些情況下，需要進行更詳細的分析以確定：最大線路電阻。
以下各節概述了如何計算最大線催化傳感器、回路供電傳感器和變送器的電阻
由系統57供電。電纜指南見第11.3節選擇催化傳感器催化傳感器電纜的最大線路電阻不同根據安裝的傳感器類型的電流和電壓要求。
它還受到端子S之間允許的最大10V電壓的限制以及在現場接口/中繼卡處的NS。
最大線路回路電阻計算如下：
10-VsRL=s
式中：RL=總線路電阻（歐姆）Vs=傳感器電壓（V）
s=傳感器電流（A）
11.5 4-20mA回路供電傳感器：
4-20mA回路供電電纜的最大線路電阻
傳感器隨傳感器類型的電壓驅動要求而變化
安裝。它還受到20V最大環路驅動電壓的影響。
最大線路回路電阻計算如下：
20-VsRL=0.025
式中：RL=總線路電阻（歐姆）Vs=最小傳感器工作電壓（V）
SENSOR INSTALLATION
11.1 General
Always install the sensors in accordance with the Sensor Operating
Instructions.
In general, sensors for lighter than air gasses should be located at a
high level and sensors for heavier than air gasses should be located at
a low level.
Do not install the sensors:
a. Where the normal air flow may be impeded.
b. In corners of rooms where static air pockets may exist.
c. Near sources of heat such as convector heaters.
Do install the sensors:
a. As close as possible to the potential source of gas to be detected in
order to give the maximum possible warning.
b. So that they are accessible for maintenance work.
11.2 Sensor Line Resistance
Sensors should be located such that the line resistance of cable does
not exceed the maximum permitted. The table gives a quick guide to
the maximum cable lengths permitted for specific sensors, when
connected by stranded copper conductor cables of various sizes to a
System 57 running at the minimum dc input voltage.
The figures in the table provide a useful reference guide to maximum
cable lengths, however, in many circumstances longer cable runs can
be used. eg. Where the dc input voltage is higher than the minimum. In
these circumstances a more detailed analysis is required to determine
maximum line resistance.
The following sections outline how to calculate the maximum line
resistance for catalytic sensors, loop powered sensors and transmitters
powered from the System 57. See Section 11.3 for a guide on cable
selection.Catalytic Sensors
The maximum line resistance of cabling for a catalytic sensor varies
with the current and voltage requirements of the type of sensor installed.
It is also subject to a maximum of 10V permitted across terminals S
and NS at the Field Interface/Relay Card.
Maximum line loop resistance is calculated as follows:
10 - Vs
RL =
I
s
Where: RL = Total Line Resistance (ohms)
Vs = Sensor Voltage (V)
I
s = Sensor Current (A)
11.5 4-20mA Loop Powered Sensors:
The maximum line resistance of cabling for a 4 - 20mA loop powered
sensor varies with the voltage drive requirements of the type of sensor
installed. It is also subject to a 20V maximum loop drive voltage.
Maximum line loop resistance is calculated as follows:
20 - Vs
RL =
0.025
Where: RL = Total Line Resistance (ohms)
Vs = Minimum Sensor Operating Voltage (V)
