24  S P I R I T
IT
  F L O W- X   INS T R U C T I O N   M A N U A L   |   I M/ F L O W X - EN 
 
Pulse inputs 
When connected to a device that resides in a hazardous 
area, safety barriers or galvanic isolators may be 
required to be interposed between the device and the Spirit
 IT
 
Flow-X flow computer. Refer to the device documentation for 
adequate information. 
 
Each digital channel can be configured as a pulse input. 
Depending on the type of pulse signal a single- or dual pulse 
input will be allowed for each flow module. Each flow module, 
depending on the hardware version,  supports one or multiple 
pulse input.(single or dual). 
 
To accommodate for different type of pre-amplifiers each pulse 
input channel supports two threshold levels for signal activation. 
For channels 1 through 8 the threshold level is selectable 
between 1.25 V and 12 V and for channels 9 through 16 between 
3.6V and 12 V. The default is 12 V for all 16 channels. 
Both single and dual pulse inputs are supported. In dual pulse 
mode, ISO 6651 pulse integrity checking at level B is always 
enabled. Level A support (correction) may optionally also be 
enabled. 
 
It is common practice to use pre-amplifiers to condition signal 
level from the meter pickup-coils. The following figures illustrate 
typical wiring when using pre-amplifiers. 
 
 
Figure 6-12 Pre-amplifier with open-collector output 
 
 
Figure 6-13 Pre-amplifier with voltage output 
 
Time period inputs 
When connected to a device that resides in a hazardous 
area, safety barriers or galvanic isolators may be 
required to be interposed between the device and the Spirit
 IT
 
Flow-X flow computer. Refer to the device documentation for 
adequate information. 
 
Each digital channel can be configured as a time period input, 
typically used to connect densitometers (also called density 
transducers or density meters) and specific gravity transducers.  
Each Flow-X/M module supports 4 time period inputs. 
 
Time period inputs have to be connected to one of 16 digital 
channels provided by each flow module. Make sure that the used 
digital channel number has been set up properly in the Spirit
 IT
 
Flow-X configuration. 
 
For Solartron densitometers a 1 micro-Farad capacitor is 
required between the pull-up resistor and the digital channel as 
shown in the following figure. 
 
 
Figure  6-14  Solartron  densitometer  connection  (loop  powered  by 
Flow-X) 
 
Note : When the loop is externally powered a second 1 uF 
capacitor needs to be installed between the Solartron ‘SIG-‘ and 
the Flow-X ‘Common‘. The capacitor should not have a polarity 
(+/-), electrolytical capacitors should not be used. 
 
Digital outputs 
When connected to a device that resides in a hazardous 
area, safety barriers or galvanic isolators may be 
required to be interposed between the device and the Spirit
 IT
 
Flow-X flow computer. Refer to the device documentation for 
adequate information. 
 
Each digital channel can be configured to operate as a digital 
output in which case it acts as an open collector. When the 
digital output is activated, the digital signal is connected to the 
flow computer common ground. 
 
 
Figure 6-15 Internally powered digital output