The Channel Expansion ModuleThe dataTaker 500/600 series loggers can be expanded by connecting 1 or 2 Channel Expansion Modules (CEM-AD) in a daisy chain configuration. The Channel Expansion Module (CEM-AD) has a channel capacity as follows 10 analog input channels, implemented as 10 differential or 30 single ended 20 digital input channels, implemented as TTL/CMOS/Voltage free contact 10 digital output channels, implemented as 5 contact closure outputs and Installing the Channel Expansion ModuleOne or two Channel Expansion Modules (CEM-AD) can be connected to a dataTaker 500/600 series logger. The connection between the dataTaker 500/600 series loggers and the Channel Expansion Modules is via 25 pin connectors located at one end of the logger, and at each end of the Channel Expansion Modules. The data logger and the modules are interconnected by 25 core cable. Each cable must not exceed 50 cm (20 ins) in length, and the total length of cables including the length of the logger and modules must not exceed 2 metres (6 feet). Note: The Channel Expansion Modules must not be connected to the dataTaker while the logger is powered. Disconnect external power and all batteries from the dataTaker before connecting the Channel Expansion Module to the logger. The Channel Expansion Module is designed as a permanent fixture for the dataTaker, and must not be disconnected until power and all batteries are disconnected. The Channel Expansion Module is powered by the dataTaker, and does not require a separate power supply. The footprint size of the Channel Expansion Module is identical to that of the dataTaker, and is compatible with the range of dataTaker enclosures as follows Large Industrial Enclosure - accommodates one dataTaker and one Channel Expansion Module (CEM-AD) Small Industrial Cabinet - accommodates one dataTaker and two Channel Expansion Modules (CEM-AD) The dataTaker and Channel Expansion Module(s) can also be fitted into any suitably sized enclosure, either side by side or end to end depending on the shape and size of the enclosure. When using thermocouples with the dataTaker and the Channel Expansion Modules, it is recommended that the dataTaker and Channel Expansion Modules be fitted into a suitable metal enclosure to avoid thermal gradients across the modules. A metal enclosure also protects against magnetic and electrical interference on the modules and interconnecting cables. Channel Expansion Module NumberThe Channel Expansion Modules (CEM-AD) do not have a hardware address. Once the interconnecting cable is fitted and the dataTaker is powered up, each Channel Expansion Module available is identified and numbered in software as module 1 and module 2. The Channel Expansion Module connected to the dataTaker becomes module number 1, and the next Channel Expansion Module becomes module number 2. To confirm the connection of a Channel Expansion Module to the dataTaker, enter the TEST command from DeTransfer as follows TEST The TEST command will return a report as follows dataTaker 526 Ver 7.00 Using DeLogger, the TEST command is run by clicking on the TEST button on the main toolbar of DeLogger, or by selecting ResetÖ under the dataTaker menu..
The first line of the TEST report contains information about the configuration of the dataTaker (See Section III ñ TEST Command) and version of firmware. The digit 6 is appended to the dataTaker xxx for each Channel Expansion Module that is connected to the logger. Connection of the Channel Expansion Module(s) to the dataTaker 500/600 series loggers is illustrated below.
Figure 125 - Channel Expansion Module Connection Commanding the Channel Expansion ModuleThe Channel Expansion Module (CEM-AD) provides increased channel capacity for the dataTaker 500/600 series loggers. In general the channel and signal measurement specifications of the Channel Expansion Module (CEM-AD) are the same as the dataTaker model to which it is connected. These channels and signal types are commanded in the same manner as for the dataTaker to which the Channel Expansion Module(s) are connected. The Channel Expansion Module has a relay multiplexer for the analog input channels, similar to that for the dataTaker 505,515, 605 and 615. If the Channel Expansion Module is connected to a dataTaker 500 or dataTaker 600 data logger, then the module has a maximum input voltage of ±2500 mV and a common mode range of ±3.5 Volts. If the Channel Expansion Module is connected to a dataTaker 505, dataTaker 515, dataTaker 605, dataTaker 615 data logger, then the module has a maximum input voltage of ±100 Volts and a common mode range of ±100 Volts. The Channel Expansion Module is capable of withstanding in excess of 500 Volts for 50 mS, or 100 Volts continuously, on any unselected analog input channel. Module NumberThe commands used to specify channels of the Channel Expansion Module (CEM-AD), and channel options for channel configuration, follow the same conventions as those used for the dataTaker. However each command directed to a Channel Expansion Module is prefixed by a module number and a colon character as follows n:channel type(channel options) where n: the CEM number, either 1 or 2. Using DeTransfer, channels on a Channel Expansion Module are specified as follows 1:6TK 2:1..3DS which specifies a K type thermocouple connected to analog channel 6 of CEM number 1 digital state channels 1 through 3 of CEM number 2 Using DeLogger,
channels on the CEM-AD are selected in the Program Builder as part of a program as follows Analog Channels: firstly select any analog channel of the logger, say analog channel 10, and attach the sensor type that is connected to the target channel on the CEM then reassign this channel to the CEM by right clicking on the new ëpseudoí channel icon, and select Channel Options:Channel Number:CEMn:channel number Digital Channels: firstly select any digital channel of the logger, say digital channel 1, and select the state or counter input type that is connected to the target channel on the CEM then reassign this channel to the CEM by right clicking on the new ëpseudoí channel icon, and select Channel Options:Channel Number:CEMn:channel number The raw data returned for channels of the Channel Expansion Module have the module number prefixed to the channel identification as follows 1:6TK 156.65 Deg C Internal ChannelsThe Channel Expansion Module (CEM-AD) has two internal channels, which are used as reference channels when monitoring thermocouples. The two internal channels are the module temperature which is sensed by a LM35 monolithic temperature sensor, and an electrical zero channel. These internal channels are identified in the general format as follows n:1%LM35 internal temperature channel n:2%V electrical zero channel where n is the module number. Over Voltage ProtectionThe Channel Expansion Module (CEM-AD) does not include built in energy absorbing lightning protection. However all analog input channel terminals except for the Analog Return terminals are capable of withstanding 1.5KV for 10µS, 500V for 50mS and 100V indefinitely. The Analog Return terminal can withstand only 5% of these voltages. The above withstanding voltages apply only to unselected channels. While a channel is selected for reading (a process that typically takes 30mS), these withstanding voltages are reduced to the common mode voltage range of the dataTaker as follows dataTaker 500 and 600 ±5 Volts relative to ground dataTaker 505, 515, 605 and 615 ±100 Volts relative to ground In applications where scanning is infrequent (say not more than every 3 hours), the probability of a scan being co-incident with a lightning strike is very low. Where lightning is frequent, it is strongly recommended that external energy absorbing lightning protection be wired to each sensor line. Further, it is recommended that the dataTaker 505, 605, 515 or 615 loggers which have higher withstanding voltages be used. Using ThermocouplesThe Channel Expansion Module (CEM-AD) fully supports thermocouples for cold junction compensation and zero voltage compensation. The Channel Expansion Module has a LM35 temperature sensor located so that it senses the temperature of the analog input channel screw terminals. These terminals are the thermocouples reference junction. The dataTaker will automatically measure the Channel Expansion Module temperature and electrical zero when scanning a thermocouple channel on the module. These values are then used for reference junction compensation. The accuracy of thermocouple measurement is dependent on the isothermal condition of the reference junction. If a temperature gradient develops between the modules temperature sensor and the input terminals, the error will approximately equal the temperature difference. The module utilises relays for channel selection and digital output. These are a source of heat and each relay dissipates 150mW when switched on. For maximum thermocouple accuracy, ensure that these relays are not left on unnecessarily. A not so obvious reason that a relay may be left on is that the last channel in a scan remains selected if Parameter15 is set to 1 or 2. This can be resolved if P15 is set to zero, or a dummy channel is placed at the end of the Schedule. A good choice would be 1%V(M18:156,W). Power ConsumptionThe Channel Expansion Module (CEM-AD) consumes very little power if the dataTaker to which it is attached is allowed to sleep. While scanning channels on the Channel Expansion Module, the current drawn from the dataTaker will increase to approximately 60mA. Additional current is required if the digital output relays are switched on. Each of the five relays will draw 35mA, however these relays are automatically switched off when the dataTaker sleeps. A summary of current draw is tabulated below:
External ExcitationThe Channel Expansion Module (CEM-AD) can power or excite sensors from the Excite (]) terminal of the analog channels. Excitation can be provided either by the standard current and voltage sources, or by an external power source. For sensors that require non-standard powering or excitation, an External Excitation input terminal is able to direct power to the Excite (]) terminal of selected analog channels. This option must be enabled by moving a jumper to the outer two pins on a three pin header. For location details of the jumper See Section I - Construction of the Channel Expansion Module. The normal position of the jumper (between the inner two pins) provides the standard dataTaker 250.0 µA, 2.500 mA or 4.5V excitation. If the external excitation option is selected these standard excitations are not available on any channel of module. Care must be taken in assigning channels. If for example an Expansion Module is wired with a four wire RTD, and several bridges requiring 12 Volt excitation, then the 12 Volt would be applied to the RTD when it is scanned. The RTD would probably be damaged. |
Page ContentSection 1Construction of the dataTaker 50 Construction of the dataTaker 500 600
Section 2Powering Sensors from the dataTaker The RS232 COMMS Serial Interface Measuring 4-20mA Current Loops Measuring Frequency and Period Measuring Temperature with Thermocouples Measuring Temperature with RTDs Measuring Temperature with IC Temperature Sensors Measuring Temperature with Thermistors Measuring Bridges and Strain Gauges Measuring Vibrating Wire Strain Gauges Installing The Panel Mount Display
Section 3Communication Protocols and Commands Entering Commands and Programs |
