An Improved Vehicle Detection Algorithm Based on Multi-Intermediate State Machine

Table 1

Technical parameters of HMC1022.

Characteristics	Conditions	Min.	Type	Max.	Unit
Bridge supply	Vbridge referenced to GND		5	25	Volts
Bridge resistance	Bridge current = 5 mA	800	1100	1300	Ω
Operating temperature (1)	HMC1021S, 1021Z, and 1022	−55		150	°C
	HMC1021D	−55		300
	Storage temperature (1)	Unbiased	−55		175	°C
Field range (1)	Full-scale (FS), total applied field	−6		+6	Gauss
Linearity error (1)	Best fit straight line ±1 gauss		0.05		(%) FS
	±3 gauss		0.4
	±6 gauss		1.6
Hysteresis error (1)	3 sweeps across ±3 gauss		0.08		(%) FS
Repeatability error (1)	3 sweeps across ±3 gauss		0.08		(%) FS
Bridge offset	Offset = (OUT+)–(OUT−), field = 0 gauss after set pulse, Vbridge = 5 V	−10	±2.5	11.25	mV
Sensitivity	S/R current = 0.5 A	0.8	1.0	1.25	Mv/V/gauss
Noise density (1)	Noise at 1 Hz, Vbridge = 5V		48		nV/Hz
Resolution (1)	Bandwidth = 10 Hz and Vbridge = 5V		85		ugauss
Bandwidth (1)	Magnetic signal (lower limit = DC)		5		MHz
OFFSET strap	Measured from OFFSET + to OFFSET-	38	50	60	Ω
OFFSET strap Ω tempco (1)	TA = −40 to 125°C		0.39		(%)°C
OFFSET field (1)	Field applied in sensitive direction	4.0	4.6	6.0	mA/gauss
Set/reset strap	Measured from S/R+ to S/R−	5.5	7.7	9	Ω
Set/reset current	2us current pulse, 1% duty cycle	0.5	0.5	4.0	Amp
Set/reset Ω tempco (1)	TA = −40 to 125°C		0.37		(%)°C
Disturbing field (1)	Sensitivity starts to degrade. Use S/R pulse to restore sensitivity	20			Gauss
Sensitivity tempco (1)	TA = -40 to 125°C Vbridge = 5 V	−0.32	−0.3	−0.28	(%)°C
	Ibridge = 5 mA		−0.06
Bridge offset tempco (1)	TA = -40 to 125°C no set/Reset		+0.05		(%)°C
	Vbridge = 5 V with set/reset		+0.001
Resistance tempco (1)	Vbridge = 5 V, TA = –40 to 125°C		0.25		(%)°C
Cross-axis effect (1)	Cross field = 1 gauss (see AN-205) Happlied = ±1 gauss		+0.3		(%) FS
Max. exposed field (1)	No perming effect on zero reading			10000	Gauss
Set/reset (1)	S/R current ≥ 0.5 amps			30	uV