Tanklevel

Tank level meter
Status	Stable
menuconfig	Applications->Tank level meter
Pinning	yes
Ecmd	yes
Depends on	ECMD, Clock, ADC, Cron (optional)
Code	https://github.com/ethersex/ethersex/tree/master/services/tanklevel

Tanklevel provides an application for measurement of tank levels by hydrostatic pressure.

Internals

You need an aquarium air pump, some kind of pipe/tube, a Freescale MPX5050DP pressure sensor and an relay for the pump. Parameters are configurable by ECMD and stored in EEPROM.

Configuration

 │ │                  (0) ADC channel                                    │ │  
 │ │                  [ ] Measure on system startup                      │ │  
 │ │                  [ ] Measure at 12 am and 12 pm                     │ │  
 │ │                  [ ] Inverted pump output                           │ │  
 │ │                  [ ] Check lock input                               │ │  
 │ │                  [ ] Inverted lock input                            │ │  
 │ │                  [ ] Inline tank level                              │ │  

• ADC channel - ADC channel that is connected to the MPX5050DP pressure sensor.
• Measure on system startup - Start initial measurement at system startup.
• Measure at 12 am and 12 pm - Start measurement at fixed time. Can be changed in services/cron/cron_static.c.
• Inverted pump output - Output pin for pump is inverted.
• Check lock input - Check lock pin before measurement and wait if needed. This is used to delay the measurement e.g. if the oil burner is running.
• Inverted lock input - Lock input pin is inverted.
• Inline tank level - Inline a page to query the tank level.

Pinning

Example pinning from pinning/hardware/netio.m4:

ifdef(`conf_TANKLEVEL', `
  pin(TANKLEVEL_PUMP, PC3, OUTPUT)
')
ifdef(`conf_TANKLEVEL_LOCK', `
  pin(TANKLEVEL_LOCK, PA2, INPUT)
')

Meaning:

• TANKLEVEL_PUMP - output pin for driving the pump relay
• TANKLEVEL_LOCK - optional pin for external lock signal (see Configuration)

Mechanical setup

                   +-------+
                   |Sensor |
                   +---+---+
                       | +--------+
       +---------------+-+  Pump  |
       |                 +--------+
+------+------+
|      |      |
|      |      |
|------|------|
|      |      |
|      |      |
|      |      |
+-------------+
     Tank

See the following example:

Electrical setup

Electrical setup is quite simple. Connect the TANK_PUMP port with an relay (usually via an Transistor as current amp) and the output of the Sensor with the selected ADC channel (have a look at the datasheet for power supply decoupling and output filtering). Select a optimal Vref for the ADC if possible. Schematic could look like this:

Parameters

Parameters can be viewed/set by ECMD commands:

• sensor_offset - zero offset of the pressure sensor in mV
• med_density - medium density in g/ltr (default of 840 for fuel oil)
• ltr_per_m - Ltr per meter tank level
• ltr_full - Tank capacity in ltr
• raise_time - Pump time (in 1/50 secs)
• hold_time - Hold time before measurement (in 1/50 secs)

SNMP support

If SNMP is enabled the level can be queried by this OID's:

• .1.3.6.1.4.1.2021.13.23.4.0 = INTEGER: current level in ltr
• .1.3.6.1.4.1.2021.13.23.4.1 = INTEGER: tank capacity in ltr
• .1.3.6.1.4.1.2021.13.23.4.2 = INTEGER: timestamp of last measurement (unix date)
• .1.3.6.1.4.1.2021.13.23.4.3 = STRING: timestamp of last measurement (clear text)