The dataTaker 50 has 5 digital channels, and the dataTaker 500/600 series loggers have 4 digital channels. The channels are bi-directional TTL/CMOS compatible, and can be used for digital inputs, for digital outputs and for low speed (10 Hz) counting. The Channel Expansion Module has 20 TTL/CMOS compatible digital input channels, and 10 digital output channels of which 5 are implemented as open collector outputs and 5 are implemented as relays. The digital channels cannot be used for counting. The digital input channels can be used in a variety of ways as follows monitoring the logic state of bit inputs monitoring the logic state pattern of byte inputs low speed counting to 10 Hz, 16 bit range, presettable (See Section III ñ The Counter Channels) detecting digital events to trigger Schedules (See Section III ñ Schedules Triggered by Digital Events) detecting count events to trigger Schedules (See Section III ñ Schedules Triggered by Counter Events) detecting digital state for conditional trigger (See Section III ñ Schedules Triggered While Condition) Note 1 : The digital channels are powered off when the dataTaker is in the low power mode. Therefore the digital input channels cannot be used for counting, or detecting events to trigger Schedules, during low power mode operation. Note 2 : The digital channels of the dataTaker are bi-directional, and cannot be used to monitor inputs if they have previously been used as outputs and left switched ON. The channels can be used to monitor digital inputs only if their output state is OFF. Analog input channels can also be used to monitor digital state. Analog State compares input voltage with a definable threshold to determine logic state. Analog State inputs can be differential or single ended, and cannot be used for counting. Digital State InputsThere are several types digital inputs, depending on the type of channel and whether the channels are used as bit or byte inputs. These are detailed in the table below
Reading Digital Bit InputsDigital bit input channels are specified in a schedule list in the format nDS and n..mDS where n is a single digital channel If the digital input channels are located on a Channel Expansion Module, then the module number precedes the channel number(s). Using DeTransfer, digital bit input channels are read using the commands for example BEGIN which returns data for the digital bit inputs every minute. Using DeLogger, digital bit input channels are selected in the Program Builder as follows
The data returned by reading digital bit inputs is either 1 or 0, indicating whether the input is high or low respectively. When digital bit inputs are averaged (See Section III ñ Statistical Sub Schedule), data is returned in the range of 0.00 - 1.00. This proportionally represents the number of times that the input was high when sampled during the averaging period. Digital bit averaging can be used as a measure of the duty cycle of the digital inputs. Reading Digital Byte InputsThe dataTaker is also able to read the digital input channels as byte inputs. Digital byte inputs are implemented as groups of successive digital bit input channels. The digital byte command can be used to read groups of digital input channels simultaneously, returning a decimal value representing the bit pattern of digital inputs. Digital bytes are read beginning at a specified digital input channel number, for the next 8 successive digital inputs. If there are fewer than 8 digital inputs beyond the first digital channel (as will be the case for the dataTaker) then the byte is returned only for those digital channels present. The digital byte input is specified in a Schedule list by the general format nDB(mask) where n is the first channel to begin reading the byte The digital byte input channel number n is defined as the first digital bit input channel to be read. If the digital input channels are located on a Channel Expansion Module, then the module number precedes the channel number(s). Using DeTransfer, digital byte inputs are read using the commands for example BEGIN returns the byte for all digital input channels of the dataTaker starting from digital input channel 1, and BEGIN returns the byte for digital input channels 3, 4 and 5 of the dataTaker 50, or digital input channels 3 and 4 of dataTaker 500/600 series loggers. Digital Byte MaskThe optional digital byte mask allows individual digital input channels within the group to be selected as follows channels associated with set bits in the mask are included in the byte input channels associated with clear bits in the mask are not included in the byte input The relationship between the bit number in the mask and the digital channels is below Mask bit 8 7 6 5 4 3 2 1 The mask is specified as a decimal value equivelent to the required bit pattern. The mask value is the sum of the decimal weighting for each bit, which are as follows Mask bit 8 7 6 5 4 3 2 1 Some examples of mask values and associated bit patterns follow 3 0 0 0 0 0 0 1 1 If a mask is not specified, then the mask defaults to 255 and all channels from the nominated first channel are included in the byte. The range of the data returned by reading the full byte is as follows dataTaker 50 0 – 31 dataTaker 500/600 series loggers 0 – 15 Channel Expansion Module 0 ñ 255 When digital byte inputs are averaged, data is returned in the range dataTaker 50 0.00 – 31.00 dataTaker 500/600 series loggers 0.00 – 15.00 Channel Expansion Module 0.00 ñ 255.00 This average represents a weighted proportion the number of times that the individual digital inputs were true or high when sampled during the averaging period. Using DeTransfer, masked digital byte inputs are read using the commands for example BEGIN will return the byte beginning at digital input channel 1, and masks to include the first three channels 1, 2 and 3. DeLogger does not directly support digital bytes, however these can be read using the User channel in the Program Builder as follows
Analog State InputsThe analog input channels of the dataTaker can be used to monitor logic state using the Analog State function. Differential or single ended input voltage levels are measured and compared to a user definable threshold to determine the logic state. In contrast to TTL/CMOS compatible logic state inputs where the logic thresholds are <1.5 Volt for 0, and >3.5 Volts for 1, threshold for the Analog State input type is variable and is defined as a voltage in the range of -2500 mV to +2500 mV. Analog State does not support byte inputs, or counters, and cannot be used to trigger Schedules. If the input voltage is greater than the ±3.5 Volt common mode range of the dataTaker, then it is treated as a 5 Volt level. For threshold comparison the input is treated as logic 1, and provides compatibility with TTL and CMOS inputs. Analog State of higher voltages, such as 24VDC industrial logic, can also be measured by externally attenuating the signals before connection to the logger. Reading Differential Analog State InputsWhen Analog State is to be measured for differential inputs, the voltage is applied between the +ve and ñve terminals of the analog input channel (See Section II - Measuring Analog State). The measured differential voltage is compared with the threshold voltage which is defined as a channel option for the channel, and the Analog State is evaluated as follows if the measured voltage is less than the threshold voltage, if the measured voltage is greater than or equal to the threshold voltage, Differential Analog State input channels are specified in a schedule list by the general formats nAS(threshold) and n..mAS(threshold) where n is a single differential AS channel If the analog input channels are located on a Channel Expansion Module, then the module number precedes the channel number(s). The threshold voltage must be defined in the range of -2500 mV to +2500 mV. If a threshold voltage is not defined, then the threshold voltage defaults to 2500 mV. Using DeTransfer, differential Analog States are measured by the commands for example BEGIN which instructs the dataTaker to measure analog states every 2 minutes as follows compare the differential voltage on channel 1 with the default 2500 mV threshold compare the differential voltage on channel 7 with a threshold of 1000 mV The dataTaker returns logic 0 if the measured voltage is less than the threshold, and returns 1 if the measured voltage is greater than the threshold. Note that different channels can have different thresholds. Using DeLogger, differential Analog States can be measured by the following Program Builder program. The analog connection and threshold are defined in the Analog State dialog which opens when you have selected the channel and input type
Reading Single Ended Analog State InputsWhen Analog State is to be measured for single ended inputs, the voltage is applied between the +ve, The measured single ended voltage is compared with the threshold voltage, which is defined as a channel option to the channel type, and the Analog State is evaluated as follows if measured voltage is less than threshold voltage, then logic 0 is returned if measured voltage is greater than threshold voltage, then logic 1 is returned Single ended Analog State input channels are specified in a schedule list in the general formats n T AS(threshold) n+AS(threshold) nñAS(threshold) and nT..mTAS(threshold) nT..m+AS(threshold) nT..mñAS(threshold) where n is a single ended AS channel Note that the dataTaker 50 does not support the excite terminal as an input terminal. If the analog input channels are located on a Channel Expansion Module, then the module number precedes the channel number(s). Threshold voltage is defined in the range of -2500 mV to +2500 mV. If a threshold is not defined, then the threshold voltage defaults to 2500 mV. If the single ended Analog State input is referenced to SE REF, then this must be specified as a X (eXternal reference) channel option as follows n+AS(threshold,X) If this option is not specified, then the single ended Analog State is measured with respect to Analog Return. Using DeTransfer, single ended Analog States are measured by commands for example BEGIN which instructs the dataTaker to measure analog states every 10 minutes as follows compare the single ended voltage on channel 1+ and Analog Return, with the default 2500 mV threshold compare the single ended voltage on channel 3+ and Analog Return, with a threshold of 1000 mV compare the single ended voltage input to channels 9ñ and SE REF with a threshold of ñ2500 mV Using DeLogger, Analog States can be measured by the following Program Builder program. The analog connection and threshold are defined in the Analog State dialog which opens when you have selected the channel and input type
Gray Code ConversionThe digital input channels of the dataTaker data loggers also support the Gray code binary system. Gray Code is often used for wind direction indicators and shaft encoders which have multi bit digital outputs. The principal of Gray code converters is that only one bit-changes for each increment. This eliminates false intermediate codes that could occur in natural binary conversion. The dataTaker implements Gray code conversion as Intrinsic Function F7, which is attached to a channel variable as a channel option. (See Section III - Scaling Data ñ Polynomials, Spans and Functions) The following example illustrates programming from DeTransfer for a 6 bit wind direction sensor. Using a dataTaker 50 the 5 digital input channels are used as the first 5 bits of the encoder output, and an analog state is used for 6th bit and is the highest order bit. BEGIN Channel Expansion Modules have 2 full 8 bit byte channels available. Therefore a 6 or 8 bit Gray code can be read directly. However if a 6 bit Gray code is used, then the 7th & 8th bits must be grounded or the first 6 bits masked by 63 (00111111). Digital Event InputsThe digital input channels of the dataTaker can also be used to detect external digital events, which can then be used to trigger Schedules. A digital event may be defined to be a negative transition, a positive transition, or both. The use of digital events for triggering Schedules is discussed in Section III - Schedules Triggered by Digital Events. The digital input channels of the Channel Expansion Modules cannot be used to trigger Schedules. Digital While InputsThe digital input channels of the dataTaker can also be used to monitor external digital conditions, and use these conditions to control the triggering of Schedules only while the particular digital input is true or high. Use of digital input channels for conditional triggering of Schedules is discussed in Section III - Schedules Triggered While Condition. The digital input channels of the Channel Expansion Modules cannot be used for conditional scheduling. |
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 |
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